Elves I have a little nostalgia for, not my favorite creature type or playstyle, but they are what I started playing magic with so I decided to try and make a competitive elf deck for Modern.
The heart of the deck is just having tons of 1 mana costing ramp creatures like Llanowar Elves, Elvish Mystic and Heritage Druid really early, ideally playing Elvish Archdruid turn 3 or 4 for even more ramp, ultimately giving tons of counters to Joroga Warcaller, using Immaculate Magistrate to power up everything, then playing Craterhoof Behemoth or activating Ezuri, Renegade Leader and swinging for some insane amount that will in most cases rip through your opponent's life total like paper. It's a pretty straightforward ramp and overrun strategy, but there are a few other techniques worth noting.
Regal Force is a great card for tribal elves, just letting you draw an insane amount of cards to speed up the deck. It's fine as a 2 of, as it can easily be searched out via Summoner's Pact and Genesis wave.
Summoner's Pact and Genesis wave are just awesome. With the amount of mana you're producing in this deck, the 4 mana to use Summoner's Pact at your next upkeep is almost never a problem unless your opponent wraths the board after you play it, which you shouldn't let happen in the first place. Better to use the pact at the end of your opponent's turn for safety. Genesis Wave you can use to essentially spill out a quarter of your deck effortlessly. I personally prefer waiting to use this until Craterhoof Behemoth is in your hand, due to there being no means of giving all your creatures haste. Generally a bad idea to risk losing the effect of the Behemoth on your entire board, but if you have enough potential attackers out already then go nuts.
Elvish Promenade I don't like as a 4 of because I'm not a fan of opening the game with a mid game card in my hand. But as a 3 of, you'll more than likely see it at some point and doubling your elf count is insane, giving more fuel to cards like Elvish Archdruid, Regel Force and Craterhoof Behemoth.
Nissa's chosen is here as a 1 of solely because I run Nissa Revane in Sideboard. I have Nykthos in my land base to give it a little more purpose, as the 2 extra devotion is always nice and when Nissa can grab him he's a nice free elf to have.
The sideboard here is essentially just dealing with decks that can stop the rampage. Burn is the most notable weakness to ramp decks, and so Asceticism gives them a means of hiding from burn spells if it gets out early enough, not hard to do in this deck.
This doesn't handle the problem of direct burn going to your face though, which is why Nissa Revane makes an appearance to gain back an ungodly amount of life and keeping you out of direct burn's killing range for a good while.
Nature's claim is basically naturalize for one less mana that makes the opponent gain 4 life. Giving the opponent that life isn't a problem in this deck I find, since by the time you swing you're swinging for a lot more than 12 potential gained life will save them from.
Scavenging Ooze helps handle reanimator decks, eating up their grave with the insane amount of mana you have and giving you life back as well as making the ooze stronger and stronger.
Gaea's Herald adds a little more assurance of dodging counterspells than cavern of souls, especially if you use cavern of souls to cast it.
Finally, Creeping Corrosion is your best weapon against affinity decks, wiping the board clean of artifacts. a fairly straightforward card and its usefulness can't be denied.
As I said before, this deck is an experiment so please feel free to post suggestions to make it stronger!
