Okay, we need fifty life. Slight problem: you don't gain life naturally. What's worse is that it's best to have the lifegain attached to an effect that honestly does way more, narrowing choices in a significant manner. Even worse, a lot of our cards chip away at our life, so we need to outpace those.

Archangel of Thune: Jeepers mister, three life a turn? Wait, no, four. Five? What? In all honesty, three turns to gain Ayli's prerequisite ten life isn't the best but Thune here works well with all of the other lifegain cards.

Ajani Steadfast: This one is an actual three life a turn (given that Ayli is the only creature you are guaranteed to have access to), but with a few neat upsides in the name of versatility. Firstly, you can increase that number with his second ability. Second, that number gets larger as the game goes on without requiring that the same card remain on the field. Third, he can generate life the turn he comes down. Love me some Ajani.

Blood Artist: It gives you a life every time any creature dies. Later in the game you can threaten people pretty hard, a la "If you clear the board, Dave over there dies."

Gray Merchant of Asphodel: Extra points if you can resolve to a board with Grave Pact, Necropotence, and Dark Prophecy . A good card with nice scaling.

Kalitas, Traitor of Ghet: A 3/4 with lifelink that also functions as a sacrifice outlet for zombies and vampires? And he grows? Sign me up!

Liliana, Heretical Healer : Don't look at me like that; she has lifelink. Plenty of ways to buff power in this deck.

Serra Ascendant: Drop this before your life hits 29 for a one-mana 6/6 with flying and lifelink. Drop it turn one for the earliest possible Ayli activation on turn three. This is a strong card.

Sword of Light and Shadow : Three life a turn, every turn.

Trading Post: Discard some cards, get four life. Not the best use of your cards, but if you need Ayli to activate in a pinch...

Vampiric Rites: Two mana for one life? That's playable? Grab your Juju Bubbles everybody!

Vault of the Archangel: Almost zero opportunity cost since it's a land. Five mana and you get lifelink and evasion on the team. You could also leave mana up in anticipation of blocking for deathtouch.

Vizkopa Guildmage: Give that creature lifelink. Give it to a huge creature.

Westvale Abbey : This land turns into a 9/7 with lifelink. If you've gained any life at all before that, you're now in Ayli's range. Also, you have a huge indestructible demon.

Wurmcoil Engine: It can get you six life a turn right off the bat, or you could sacrifice it and its children to Ayli to immediately hit 52 life.