Amulet of Vigor - one of the cards that makes this deck really shine, eliminating the downside of many of my lands, while also giving my titans +2/0 and haste (plus an extra land!). Multiples of this ramp me really fast, and is a force to be reckoned with.

Summoner's Pact - pretty much 4 more copies of Primeval Titan or whatever creature is needed, but be careful with the upkeep (I like to account for them potentially destroying any of my lands with a Tectonic Edge or the likes)!

Manamorphose - color-fixing where the only downside is not knowing what card it "really is" when considering your hand for a mulligan. It also doubles as a pseudo-answer for Blood Moon as a happy coincidence.

Turntimber Symbiosis   - this is basically a land that doubles as a threat with any bounceland later in the game. It is very comparable to Tolaria West in functionality.

Dismember - deals with indestructible and things bigger than 3 CMC, for as little mana as and 4 life. is a very flexible casting cost.

Glittering Wish - a tutor for anything multicolored in my sideboard. I'm basically running more than a 60 card mainboard, without all the dead draws. Two slots represent quite a few completely different cards, many of which have game ending potential.

Honorable Mentions

Growth Spiral / Explore - basically capable of being a free cantrip if you have Amulet of Vigor out (or ramp as intended). Without an amulet, it can be a ramp spell that cantrips itself if you have the land plays. The main benefit to Growth Spiral over Explore is if you have any lands that can be used in response to something else, for example Sejiri Steppe for protection of a creature, any bounceland as protection against land removal, or an activated Valakut, the Molten Pinnacle that you can use as removal for your opponent's creatures/planeswalkers. You can also use it for extra information in response to a Simic Growth Chamber trigger, allowing you to bounce a different land, or sneak in the one in your hand to reuse, etc. The extra color restriction can sometimes backfire, so it is a slight trade-off.

Eladamri's Call - Even though this isn't quite as good as Summoner's Pact in most situations, it is actually a pretty good turn 2. It lets you tutor for any creature, which is often the missing piece in the puzzle.

Pollen Lullaby - slows down aggro and acts as a psuedo-scry. If you win the clash, this can basically buy you two turns. Since our curve is generally higher than most decks, as long as you don't hit a land, you have a decent chance of winning the clash. Courser of Kruphix gives some nice information on timing of when to use this card sometimes.

Ancient Stirrings - basically another land, but sometimes this can find an Amulet of Vigor (around 33% chance for finding amulet T1 if none in opening hand). It's also basically a coin flip (55%) for finding a green bounceland, with less than 5% chance of fizzling (finding nothing colorless).

Force of Vigor - Very solid removal for artifacts and enchantments. It can even be cast against things like Blood Moon by exiling a green card if we are unable to float enough mana. Very versatile removal that can sometimes be a 2 for 1, or a 2 for 2 at no mana cost.

Heartless Summoning - this is very comparable to Amulet of Vigor in what it does for the deck. It allows me to play my creatures faster and for less. However, unlike Amulet of Vigor it is pretty bad in duplicates, so 2 copies at most.

Vines of Vastwood - this is an option that can save my creature from removal, or be an unexpected combat trick when my opponent thinks I just have nothing left to do with my mana and attacks into my mana dorks. This is a filler card that is fairly useful both in the early and late game and is never completely irrelevant. This makes it a decent game 1 option, even though it doesn't progress my overall strategy. Since it will almost always get sided out, unless the deck you are facing is very removal happy, I tend to have better options.

Karn, the Great Creator - This guy is really good and sometimes makes his way back into the deck, he's just in an awkward spot of the mana-curve. That's where his tutoring ability is very relevant, because 4 cost is an awkward spot for this deck, as you generally jump from 3 to 5 or more relatively quickly. However, Karn, the Great Creator mitigates that with his -2 which let's you grab any artifact from your sidedeck and potentially play it in the same turn helping to have an outlet to spend your mana on. He also can be very relevant artifact hate, both with his passive and +1 which is lowkey removal for any artifacts that are or / . Look at the general sideboarding options for some of his better targets. I've found it's either him or Glittering Wish as trying to run both just uses too many slots and clutters the deck.

Primeval Titan - the main creature this deck revolves around, quite the force to be reckoned with. It often comes out as at least a 8/6 haste trample vigilance, after fetching Boros Garrison and Slayers' Stronghold with at least 1 Amulet of Vigor out (each multiple means it gets another +2/0). With an extra 2 mana or multiple amulets, I can give it doublestrike right away with Sunhome, Fortress of the Legion also.

Cultivator Colossus - This is basically Primeval Titan's big brother when your hand is mana flooded or a utility land you need is in your hand instead of your deck. It doesn't quite go infinite with bouncelands since you need to fully resolve Cultivator Colossus's ability before resolving anything else, but it is definitely a way of making the most of mana-flooding, letting you draw into things to spend that mana on.

Azusa, Lost but Seeking - Two additional land drops per turn. Super powerful in this build. She is legendary, so you never want more than 1, which is why I only ever run 1-2 copies of her. You could potential up her to 3 copies, but I definitely don't suggest 4 due to the legendary factor.

Dryad of the Ilysian Grove / Wayward Swordtooth / Mina and Denn, Wildborn / Oracle of Mul Daya / The Gitrog Monster - Dryad of the Ilysian Grove is an additional land drop every turn, mana-fixing, and a solid 2/4 body for 3 mana. It also combos with Valakut, the Molten Pinnacle as a win-condition. Wayward Swordtooth is made better with the ability to flood the board with Heartless Summoning, and the high power can help with Mosswort Bridge even if it can't attack or block. Mina and Denn, Wildborn is a fatty that can give trample, while Oracle of Mul Daya is built in card advantage and an alternative way to use our land drops. The Gitrog Monster is an additional land drop, card advantage, and a decent body all wrapped up into one package. It's also nice to have a relevant 5 CMC card to fetch with a Summoner's Pact when I fall just short of the 6 CMC Primeval Titan - the only downside is sometimes it forces me to pitch a land I'd rather not (which isn't the end of the world, since everything has duplicate "copies"/functionality for the most part).

Courser of Kruphix / Radha, Heart of Keld / Augur of Autumn / Ramunap Excavator / Oracle of Mul Daya / Vizier of the Menagerie - Courser of Kruphix is good at letting me eliminate land draws, which can really be a problem sometimes. It also is Lightning Bolt proof, which can be huge sometimes. Lifegain from lands hitting play is just icing on the cake. Augur of Autumn / Radha, Heart of Keld does basically the same thing as Courser of Kruphix, but they are geared more towards grindy control matches instead of aggro decks, since they don't broadcast info. Augur of Autumn can let you play creatures from the top of your deck as well if you have 3 creatures with different power, while Radha, Heart of Keld can pump itself up to be a sizable threat. Ramunap Excavator is slightly different from the others, as it enables to use lands from our graveyard, instead of the top of our decks. Oracle of Mul Daya is more expensive than the others, but it also lets me play an additional land every turn. Vizier of the Menagerie lets us play creatures instead of lands, so it isn't quite as good as some of the other options in most cases. Something that is also very relevant for them all is that its 2+ power can be just what's needed for that Mosswort Bridge activation.

Lotus Cobra - Lotus Cobra helps to produce extra mana of any color with all of our land drops. Lotus Cobra is more of a combo deck option, and can almost be viewed as a worse Amulet of Vigor for mana purposes. Another thing that is relevant is that its 2 power can be just what's needed for that Mosswort Bridge activation. It can also be found with a Summoner's Pact when you opponent is completely tapped out, and you could cast a Primeval Titan already, since you'll get back your two mana on the first fetch.

Arboreal Grazer / Sakura-Tribe Scout - 1 drop creatures with slightly different uses. Arboreal Grazer is actually fetchable ramp in a sense, because it can net you 1+ extra mana in a lot of situations with a Summoner's Pact (not a suggested path against interaction). It also has reach and makes a decent blocker afterwards. Sakura-Tribe Scout is a little different, since it does nothing the turn you cast it. However, the tap effect is not only reusable every turn, but it can also let you play lands as a response to actions, similar to Growth Spiral (for example Sejiri Steppe for protection of a creature, any bounceland as protection against land removal, or with an activated Valakut, the Molten Pinnacle that you can use as removal for your opponent's creatures/planeswalkers). Sakura-Tribe Scout is also capable of ramping you to a turn 4 Primeval Titan on its own, with no other acceleration in hand. It has a lot going for it, but it is a terrible topdeck, so there's some pros/cons to consider.

Elvish Reclaimer - Surprisingly, this versatile guy is really good at doing a lot of things pretty good (not really amazing at anything though). It can act as a psuedo-extra land card, a land tutor, a sizable threat to stabilize when you have nothing (pumps itself to 3/4 by finding Ghost Quarter and destroying your own land). This is a 1 drop that scales up as the game goes on, but it definitely isn't the greatest turn 1 play.

Elderscale Wurm / Empyrial Archangel / Hornet Queen - I found myself being able to cast off a Summoner's Pact for a Primeval Titan in a lot of situations against more aggro builds, only to realize it didn't matter since I was dead the next turn anyway. Elderscale Wurm and a lot of the following options help to solve that, albeit in different ways. Everything has their specific situations and pros/cons, which I will try to explain. Elderscale Wurm just makes you invulnerable to damage until it is either removed or you drop below 7 life (loss of life bypasses the protection). Empyrial Archangel has shroud, which really comes in handy against removal. One thing worth noting is that the replacement effect is not optional, so they can remove it by simply doing 8 damage to you in 1 turn, probably its biggest downside to consider. Hornet Queen is less vulnerable to targeted removal, but more vulnerable to wipes due to low CMC and toughness. However, an army of deathtouch blockers will often slow/stop the opponents deck for a bit.

Dragonlord Dromoka / Sigarda, Host of Herons - first is Dragonlord Dromoka, whose lifegain and a high toughness make it an excellent blocker, as well as a tough to deal with beater thanks to flying. It's signature ability removes all interaction during your turn (other than activated/triggered abilities). Next we have Sigarda, Host of Herons who is near impossible to remove once it is down, so using something like Cavern of Souls to make it uncounterable is often the end of control players. There's other options like Carnage Tyrant / Thrun, the Last Troll / Cragplate Baloth / Gaea's Revenge which all basically have the uncounterable and hexproof combined, but I often find the added evasion of flying (and other abilities) to be worthy of consideration.

Honorable Mentions

Tireless Provisioner / Tireless Tracker - two landfall creatures with similar functionality but slightly different uses. The first one allows lifegain or ramp, while the second offers card advantage and grows itself bigger.

Omnath, Locus of Creation - if you can somehow support his greedy casting cost in here, he is definitely worthy of inclusion. This is one of the best landfall creatures ever created, and he would do absolute wonders in here, if only his casting cost could be supported.

Battle Mammoth - A very solidly costed body with a flexible casting cost when you don't quite have enough mana for Primeval Titan. Its ability also helps with decks with lots of removal, although not as much as hexproof would.

Elvish Rejuvenator - decent "extra land" creature that lets you dig a bit, giving slightly more than a coin flips odds at finding a bounce land if needed. Almost comparable to Arboreal Grazer, except not quite as good.

Thrun, the Last Troll - the original hard to remove green threat. This guy just keeps persisting, like a cockroach that you just can't kill.

Questing Beast - surprisingly this card is another solid option for a lower CMC bomb. It makes a good blocker even as you chip away at their life points due to vigilance. It can also chip away at their swarm, or deter them from swinging with the fattty due to deathtouch.

Embodiment of Insight a pretty good card with good overall synergy with the deck.

Vhati il-Dal capable of letting you get through with damage, or all together stop their threat with its very versatile tap ability.

Ancient Greenwarden - allows us to play lands from the grave like Ghost Quarter or Nurturing Peatland allowing you to set back your opponent with your land plays for the turn or transform your mana into cards, instead of having your extra land plays being strictly ramp. It also doubles triggers on lands ETB, so things like Valakut, the Molten Pinnacle, Crumbling Vestige, Aether Hub, Mosswort Bridge, Amulet of Vigor, and Lotus Cobra all trigger twice (so do all your bouncelands, so be careful about that).

Nethroi, Apex of Death - a solid body on a 5 CMC with deathtouch and lifelink, basically a mini Wurmcoil Engine. However, Nethroi, Apex of Death really shines for its mutate ability against removal. If you have enough mana, instead of finding another Primeval Titan with your Summoner's Pact that you transmuted from Tolaria West, you can find this guy and bring back most if not all of what they removed.

Stone-Seeder Hierophant - this functions as an overpriced Amulet of Vigor which could potentially be beneficial, since it is slightly better. However, it is extremely overpriced, so it is hard to justify the cost.

Woodland Bellower - pretty decent with the variety of 3 CMC and below creatures that are viable in this deck.

Tolaria West - transmute into another Summoner's Pact for whichever creature fits your situation best. It can also become a Chalice of the Void or Engineered Explosives if either is in the deck (or any other 0 CMC sideboard card).

Valakut, the Molten Pinnacle this is actually a win-con with enough land drops and Dryad of the Ilysian Grove. Due to the Bouncelands being able to bounce themselves, you are generally able to utilize all your extra land drops on each turn, so this damage can add up really quickly. It can be used to clear the board or to do direct damage.

Vesuva - probably the best land in the deck, as it can be pretty much anything. Not so good in the opening hand, but at least it can be played as nothing (or an opponent's land if they went first) if you only have bounces and this card, allowing you to keep a hand you would have otherwise had to throw away.

Boseiju, Who Endures - One of the best utility lands for the deck, since we can easily bounce it back to hand, making it fetchable removal for artifacts, enchantments, and even troublesome lands (essentially a broader version of Ghost Quarter if you don't plan to use it on yourself).

Nurturing Peatland / Horizon Canopy - a land that can produce a different threat in the late game, or draw a good card revealed by Courser of Kruphix. This is one land that actually isn't terrible to draw when mana-flooded. You do have to be careful to not use its mana ability if you are at 7 life with Elderscale Wurm though, as that basically negates the 7 life clause.

Slayers' Stronghold / Hanweir Battlements  - some of the best utility lands for this deck. It allows your titans to come out with haste, you can't really ask for more. Slayers' Stronghold gives haste/vigilance and +2/0, which can be important with enabling Mosswort Bridge triggers. The reason for Hanweir Battlements  is to be able to give a titan haste even if you already have used its better counterpart and aren't able to Vesuva or pay for the activation. That way you can still attack with a titan that you cheated into play with say Mosswort Bridge or maybe you wanted to fetch something like Hanweir Battlements  + Valakut, the Molten Pinnacle instead. Having both as an option gives you a lot of flexibility in your plays, and makes us less susceptible to things like Surgical Extraction.

Sejiri Steppe / Sunhome, Fortress of the Legion - Sunhome, Fortress of the Legion is great to block something with deathtouch (take that Wurmcoil Engine - I live and you don't even gain life), or just double your damage. However, Sejiri Steppe accomplishes the main goal of this utility slot, which is to help your Primeval Titan live after attacking (against most decks), but it requires no investment of to activate. This slot can be unneeded in some matches, so it can definitely be sided out when it's not that relevant.

Cavern of Souls - good for control matches, and it can also be useful for colored mana when trying to hard cast more color intensive creatures like Sigarda, Host of Herons. Since I have a lot of bouncelands in here, I can change the creature type I named almost as often as I want, so this is almost like an Ancient Ziggurat that I can tap for colorless when not casting creature spells.

Ghost Quarter / Field of Ruin - land destruction that can double as another copy of a Forest if I am facing hate like Blood Moon. It's worth mentioning - don't hesitate to blow up your own lands with Ghost Quarter for landfall or The Gitrog Monster triggers - this has saved me on numerous occasions. It is actually a 3 mana land when fetched by Primeval Titan with Lotus Cobra or Tireless Provisioner out (two landfalls + green). It also allows you to draw 2 cards with The Gitrog Monster (one on the sacrifice cost, then one on the land destruction).

Turntimber, Serpentine Wood   - this is basically a land that doubles as a threat with any bounceland later in the game. It is very comparable to Tolaria West in functionality, except it cannot be fetched by Primeval Titan and is a much preferred untapped green source.

Mosswort Bridge - the most powerful digging tool and virtual advantage this deck has to offer. Cast off anything for 1 green? Yes please! Need to find some removal because they are just stalling with something stupid and annoying? Keep copying/bouncing this until you find what you are looking for. Another thing worth mentioning is Mosswort Bridge + Vesuva in conjunction with any bounceland becomes a powerful digging tool (hide multiple land drop cards/bounces/ways to play titans to get bounces until you find your answer). I've actually dug through something like 40+ cards like this in one turn (before Summer Bloom was banned - now you can probably only do 20+ semi-consistently - which is still amazing in my opinion). Also, this lets us cast Glittering Wish at instant speed if it is hidden away, so you can find instant speed sideboard answers like Abrupt Decay / Anguished Unmaking as well to cast in response, even if they aren't in your maindeck, basically giving us an answer to almost anything. I used to use this trick a lot with Batwing Brume when Splinter Twin was prevalent to just win games during their attack phase when they thought they'd won. If you are running this, it is basically required to run Slayers' Stronghold + Boros Garrison alongside it, allowing you to get to 10+ power far more consistently. Boros Garrison is the only non-green bounceland I'd suggest, and it can also be copied later via Vesuva for a Sunhome, Fortress of the Legion later. This is one that you generally want to have on the field as soon as you draw it, unlike the green counterparts. Even if it is tapped to pay for your Primeval Titan you can just fetch Vesuva to copy it. The or can also be useful for any double costed cards, like Hokori, Dust Drinker making this potentially our 5th bounceland for an early cast as an example. So in conclusion, you must run Slayers' Stronghold + Boros Garrison alongside this, and because of those mandatory inclusions, Sunhome, Fortress of the Legion becomes a decent option as well.

Urza's Saga - I've finally given in and conformed to the meta a little bit by including some copies of this card. However, I don't think it is good enough of a card that you need to run a playset. If you have to rely on Urza's Saga to find your Amulet of Vigor, your hand was kind of bad anyway. We also aren't built like your typical amulet deck's with lots of once a turn instant land plays, so amulet is not as necessary, and we are more content with lands coming in tapped if needed. It does allow for a double amulet more often (making it a solid first land), even though I still think it is over-hyped and super vulnerable to removal. You need it to stick around for 2 of your opponent's turns to actually do anything for you, otherwise it is just a colorless land that gives your opponent an enchantment to remove that can produce little creatures, also vulnerable to removal. I mainly went with it due to the ability to make construct tokens with a Mosswort Bridge fetch to get to 10 power next turn if needed, when I don't have an amulet (which works with just one copy). I also don't run Expedition Map alongside this, as I am not running enough copies to justify it, and I feel Elvish Reclaimer does a much better job at filling that slot, all things considered. If you are running 3-4 copies for whatever reason, I'd consider going 4x Simic Growth Chamber with Gretchen Titchwillow in the side (or main) for the draw my whole deck combo with 2 Amulet of Vigor.

Forest / Snow-Covered Forest - basic lands are needed, enough said. It stops Path to Exile from being as devastating, and allows some powerful interactions by targeting yourself with Ghost Quarter, along with giving hope against Blood Moon.

Selesnya Sanctuary / Golgari Rot Farm / Simic Growth Chamber / Gruul Turf - green bouncelands, the main thing this deck revolves around. It is a good idea to keep one of these in hand at all times (or a Vesuva to copy one) to make the most of your multiple land drop potential. The only time I play my last one in hand is if it means I can hard cast a bomb that I feel will get through when I untap next turn. Otherwise it is best to keep them in hand with the potential of drawing extra land cards, allowing you to "go off" in a lot of cases (considering you have either an amulet in play, or dryad/azusa in hand, and are just waiting on the other piece).

Crumbling Vestige / Aether Hub / Gemstone Mine / Tendo Ice Bridge / City of Brass / Mana Confluence / Vivid Grove - Crumbling Vestige has the benefit of coming into play tapped, so with Amulet of Vigor it is actually better than a 1 mana land (making it an auto-include as a 1-of). Also worth mentioning is that with Dryad of the Ilysian Grove and Amulet of Vigor out, it is essentially capable of becoming a Boros Garrison that doesn't need to bounce a land, perfect for cheating another land closer to 6 for the Valakut, the Molten Pinnacle activation. Gemstone Mine is probably the best of the rest, since you can use it twice then bounce it to reset its counters. Aether Hub is a strictly better version of Tendo Ice Bridge and is next in line, since you can bounce it and replay it without using the to stack multiples for later. City of Brass deals 1 damage whenever tapped and Mana Confluence allows you to pay 1 life for any colored mana, which are very important distinctions, and here's why: City of Brass will deal damage to you no matter if you have a replacement effect on it or not, so things like Yavimaya, Cradle of Growth or Dryad of the Ilysian Grove don't help you. However, since it is damage, and not loss of life, it doesn't conflict with Elderscale Wurm so you can remain at 7 life. Mana Confluence is the complete opposite, so if you use it's mana ability with Elderscale Wurm out and go under 7 life, his ability doesn't prevent it, and you are basically vulnerable again. Vivid Grove comes into play tapped, essentially making it the worst of the bunch as it can sometimes takes away strong turn 1 potential, so keep that downside in mind.

Misty Rainforest / Windswept Heath / Verdant Catacombs- or fetchlands so you can find shocklands/triomes (these also make the Blood Moon matches a little easier). Due to or being more of an "OR" instead of an "AND" on my card costs, it's possible to run non-green shocks like Godless Shrine or Hallowed Fountain instead of the 2 card combination of Temple Garden / Overgrown Tomb / Breeding Pool for basically the same playability. You need at least 3 fetches + 4 targets (2 shocks/triomes + 2 basics) for it to be worth running fetches/shocks/triomes. Otherwise, go with 5 color land options instead. Hallowed Fountain allows for greedy plays like Glittering Wish into Unmoored Ego, while godless shrine allows for Glittering Wish into Culling Ritual. You want a green counterpart to whatever support shock you choose. The green copy could be a triome as well, since you have Forest if you need an untapped manasource. The triome gives you the ability to cycle for card draw if really desired, and has slightly better mana-fixing at the cost of coming in tapped.

Honorable Mentions

Castle Garenbrig - this is decent as potential ramp if you run enough fetches + Forest Subtypes that it can consistently come out untapped. Not really worth forcing into the deck, but if you have a high land count and have the space, it is a valid option.

Temple of Plenty / Temple of Malady - tapped lands that let you scry. Since there's not a whole lot of early plays that need a turn 1 untapped land, the scry outweighs the slower land in most cases. Zhalfirin Void is another option, although I generally want the green mana source over the untapped land. If you aren't playing any early green plays like Ancient Stirrings, Zhalfirin Void may be a better option.

Khalni Garden / Radiant Fountain / Kabira Crossroads / Blossoming Sands cycle - chump blocker or lifegain slot. Sometimes that is enough to turn the tide of battle, so it isn't to be under-estimated as a utility option. I generally go with Khalni Garden / Kabira Crossroads if I have enough space (can potentially filter the with Wooded Bastion).

Blast Zone - This is more of a utility land to deal with the decks that pump out tons of low cost creatures/board presence. This is basically an Engineered Explosives attached to a land. It's biggest drawback is that it can't hit 0 cost permanents, since it enters with 1 counter on it already. You can also use it to blow up some big hard to remove threat with hexproof/shroud if you have enough mana.

Arena / Quicksand / Eiganjo, Seat of the Empire - targeted removal with their own respective pros and cons. Notably, Arena + Sejiri Steppe have decent synergy as a Primeval Titan fetch package. However, Arena not producing its own mana is the main thing holding it back, so you should consider it as more of a fetchable creature removal than a land if trying to fit it in.

Yavimaya, Cradle of Growth - This gives all my lands the ability to tap for which allows the deck to stretch it's manabase a little thinner.

Wooded Bastion / Twilight Mire / Flooded Grove / Fire-Lit Thicket - filter lands to help manafix if you have a lot of non-green double cost cards.

Reflecting Pool - this is basically a psuedo-5-color land that makes cards with multiple of the same color cost a lot easier to cast. It gets exponentially better with more multicolored lands, and is quite nice in greedy manabases like this one.

Lotus Field - capable of being a 3 mana landdrop/fetch with Amulet of Vigor, or drawing (one card) with The Gitrog Monster, so a very useful land. Since so many of our lands have utilities of their own, it gets tricky choosing what to sacrifice sometimes. Having that extra mana as an option does enable some plays that wouldn't otherwise be possible though.

First of all, when heading into game two, I usually decide what to side out first. If any of my wishes are game-ending enough to justify tutoring for them with Glittering Wish, and if broadcasting them doesn't matter, I can keep Glittering Wish mainboard (for example 2x Glittering Wish + Culling Ritual is essentially 3x Culling Ritual if I leave a copy in the side). If not, I side both out. From there, I evaluate which cards are less than optimal. Elderscale Wurm goes out against decks that don't plan to win through damage, like infect, or loss of life, etc. Things along those lines, where you take out irrelevant cards.

After all that, I decide which sideboard cards could prove useful in the match, and move them in. Afterwards, I adjust to make my sideboard as close to 15 cards as I can, whether I need to remove more "filler" slots like Manamorphose, or if I have to move in some of the "better" cards I tried to side out (dependent on the match). Manamorphose is still relevant when you suspect a possible Blood Moon or want to help ensure you can cast a greedy colored card early like Unmoored Ego.

Another option is removing some utility lands that don't really serve a purpose in the match (Cavern of Souls, Sejiri Steppe, and sometimes Ghost Quarter) depending on the deck you are facing. I do not suggest going under 25 lands though. Also worth mentioning is don't stress about getting exactly 60/15; there's times I will play with a 61 card deck in game 2 (usually against some weird homebrew where I want more options and lots of our sideboard seems relevant).

Lastly, you can always include some sneaky tech like Hokori, Dust Drinker if you have the space. If you're facing anything with a more aggro build, this particular choice isn't the best option. For example, puresteel decks can be seen as a combo deck, but they are a more aggro combo deck, where they get early board presence. Hokori, Dust Drinker is not a good option against decks like these, since they can still keep applying pressure even without mana with a quick start, and since a large majority of the meta falls into this aggro-esque category, Hokori, Dust Drinker isn't really poised as a solid sideboard option currently. However, the surprise factor of an obscure card like this definitely pays off sometimes, so that's just something to keep in mind.