Sephara, Sky's Blade is an easy swap here at $2.50. She doesn't provide as much protection as Avacyn but does protect the wallet. Avacyn is not as impactful as her dollar value suggests but the borderless variant was simply too gorgeous to not run.

Resplendent Angel - $40

As an angel token maker, Resplendent has put in work before, especially as their tokens have vigilance naturally. In comparison to Luminarch Ascension, Valkyrie Harbinger, Angelic Accord, Court of Grace and The Book of Exalted Deeds I'd put it in between Luminarch and Harbinger. While it can activate on its own, it requires 6 mana to do so which Giada and cost reducers cannot help with. It also only happens once per turn in comparison to Luminarch's every 2 mana. The 5 life requirement can also make for some missed triggers when there's only a Bishop of Wings or a Righteous Valkyrie with no Giada.Speaker of the Heavens is a one drop with similar lifegain token making strategies but would require more investment into lifegain to make sure his ability can pop off. But for under $1 it's definitely a better budget pick.

Archangel of Thune - $30

Despite getting a reprint in double masters Thune still remains stubbornly pricy. It's difficult to swap Thune out as there can be quite a few triggers in one turn, especially if you're running Soul Sisters. Norn's Choirmaster would've been an appropriate swap but recently had a sharp spike in price. A cheaper anthem like Angel of Invention or keyword anthem like Angelic Skirmisher can work in a pinch.

Gisela, the Broken Blade  ^Meld - $30

Required for melding into Brisela, Voice of Nightmares  ^{Flip  Meld  Meld}. While Bruna, the Fading Light  ^{Flip  Meld} can be played on her own, she's mostly a worse Karmic Guide. If Brisela's control mechanics are what's needed then Angel of Jubilation, Linvala, Keeper of Silence or even an Angel of Finality can work.

Tutors in mono-white are pretty rare and Recruiter is integral to the blink package. Being able to pull Stoneforge Mystic for the Swords or Starnheim Aspirant for the ramp is difficult to replace.

Stoneforge Mystic - $25

Chaining Stoneforge with Sword of Hearth and Home can become a nasty combo if left unanswered. It gives protection, ramp and equipment tutors once per turn or twice with doublestrike.

I picked this one up myself when it was at $50+ so having it drop $20 is quite nice. Untapping all lands on combat damage can give us more outs on opponents turns. The protection and forcing discard are just extra. Dowsing Dagger  ^Flip for $5 can achieve similar results by ramping us an extra 3 on hit and the Plant tokens generally are not worth worrying about.

Sword of Fire and Ice - $50

Unfortunately Fire and Ice didn't get a reprint in the list so their price is still high. While I used it to replace Rogue's Gloves or Mask of Memory, the shock is just as relevant as the draw while the protection helps cover all the colors if we're going voltron. Oftentimes there will be an annoying creature that we won't want to waste our precious removal on but can instead shock it to death.

Lightning Greaves - $10

While it's not over $20 there is an obvious subsittute here for Swiftfoot Boots. Boots has the advantage of having hexproof instead of shroud so you won't need to move it off to equip something new. However the advantage of having it at 0 equip cost can mean we move the Greaves around freely while casting spells. As mono-white doesn't have a lot of ramp, the additional 1 mana can make a huge difference between a win and a loss.

In a mono-white deck there aren't many avenues for ramping so a simple Medallion can save 10+ mana over the course of the game. Arcane Signet will serve a similar purpose.

Urza's Incubator - $20

While the price did get cut in half with the recent reprint, it's still a pricey card for a straight cost reduction. Starnheim Aspirant achieves the same thing for <$2 but is much easier to remove. Herald of War can sometimes reduce 6+ colorless when dropped which would remove the need of either Starnheim or Incubator but would be an obvious target. Substituting a cheap mana rock here can suffice like a Mind Stone or Wayfarer's Bauble.

Rhystic Buddy is a white staple and can provide tons of draw early game for 1 drop. If you're running white in your other decks then this card should be an auto-include and just hot swap it for whatever deck you're playing. Incremental draw like Tome of Legends or Eye of Vecna would be a substitute albeit a pretty poor one.

Teferi's ProtectionGC - $25

Guaranteed protection till your next turn is hard to beat. Phase out effects like Clever Concealment or Guardian of Faith and blink effects like Cosmic Intervention can protect our board state but will do nothing against combat threats coming at us for lethal. Adding in another piece such as Platinum Angel or Enduring Angel  ^Flip may help with that but is not guaranteed. If you have the funds then this should automatically go in any white deck.

Simply used as a basic ramp card in line with Mana Crypt. While it's not an immediate slot in for all decks, there's enough lifegain in Angels to offset it. Swap for a basic Plains

Cavern of Souls - $50

While it seems like an auto-include in any tribal deck playing against blue, the anti-counter ability was only useful once out of dozens of games. If your meta leans more blue and counter heavy then I would consider it. Swap for a basic Plains

Land Tax - $35

As a T1 drop, Tax can do quite a bit of work by keeping your hand filled with relevant plays, thinning the deck and making sure you make your land drops. Late game it can be a dead draw. Archaeomancer's Map at $5 can suffice as a ramp swap although it's fighting for an Angel when dropped on T3. Late game it can still provide value as you're pulling Plains for a possible Emeria Shepherd play.

Nykthos, Shrine to Nyx - $30

Late game there's a lot of devotion to white and while it doesn't provide the same burst as a Cabal Coffers with Urborg, Tomb of Yawgmoth it can generate 5-6 additional mana for a final push. While not necessary, it can make for some flashy plays and there's not really an equivalent in mono-white. Swap for a basic Plains.

Fetch Lands

Flooded Strand - $25, Arid Mesa - $15, Marsh Flats - $12, Windswept Heath - $25, Prismatic Vista - $20 (~$100 total)

Crucible of Worlds - $18

As I have a full set of fetchlands and saw the Borderless variant of Crucible of Worlds I decided to include all of them. Not only does it help with ramp and thinning the deck, when comboed with Emeria Shepherd they can provide quick recovery after a boardwipe or some game ending plays like dropping a Sigarda's Vanguard for free.