This deck's primary win conditions are a set of infinite combos (borrowed from Infinite Possibility (Elvephants)). I like these combos both because their casting cost is very low and because Simic gives me the possibility for significant mana ramp and card fetching.
Elvish Archdruid + Staff of Domination
(with 6 or more elves) allows the Archidruid to tap for mana which is fed into the staff to untap the archdruid. With enough elves out, this process produces a surplus of mana each iteration which can be used for any of the things the staff can tap for.
Intruder Alarm
+
Kazandu Tuskcaller
or Intruder Alarm + Presence of Gond
allow you to spawn an infinite number of creature tokens. The infinite number of elves created with Presence of Gond are particularly useful since they let Elvish Archdruid tap for infinite mana.
While it's only a finite combo, limited by green mana, Imperious Perfect
+
Intruder Alarm
does combo to allow many elf creatures to be put into play, which can also boost Elvish Archdruid's mana ramp.
To ensure that even bad draws quickly lead to a win condition, this deck uses Drift of Phantasms to fetch Elvish Archdruid, Intruder Alarm, Presence of Gond or Staff of Domination depending on which card the deck needs to complete one of those infinite combos. Elvish Harbinger similarly fetches a win condition but is restricted to elf cards.
Llanowar Elves and Coiling Oracle help with ramp and ensure that there are enough elves in play for the Elvish Archdruid combo, without slowing the deck down. Be sure to use Temple of Mystery to scry before playing the Coiling Oracle to make sure you draw a land, possibly by bouncing the Temple of Mystery back to your hand with Simic Growth Chamber.
The deck's backup plan, usually to buy time, is just to act as a tribal elf deck. There are 8 lords (Elvish Archdruid & Imperious Perfect each adding +1/+1 to each of the deck's 20 elves (plus tokens). It won't usually win the game, but it's surprisingly strong for a deck that's focused on getting out a winning combo.