Ajani's Pridemate

Whenever you gain life, put a +1/+1 counter on this creature.

Plains

Serra Ascendant

Lifelink (Damage dealt by this creature also causes you to gain that much life.)
As long as you have 30 or more life, Serra Ascendant gets +5/+5 and has flying.

Staff of the Sun Magus

Whenever you cast a white spell or a Plains you control enters, you gain 1 life.

Luminous Phantom

Flying
Whenever another creature you control leaves the battlefield, you gain 1 life.
If Luminous Phantom would be put into a graveyard from anywhere, exile it instead.

Lunarch Veteran

Whenever another creature you control enters, you gain 1 life.
Disturb {1}{W} (You may cast this card from your graveyard transformed for its disturb cost.)

Lunarch Veteran // Luminous Phantom

Soul Warden

Whenever another creature enters, you gain 1 life.

Rest for the Weary

Target player gains 4 life.
Landfall — If you had a land enter the battlefield under your control this turn, that player gains 8 life instead.

Hallowed Priest

Whenever you gain life, put a +1/+1 counter on Hallowed Priest.

Chaplain's Blessing

Impassioned Orator

Whenever another creature you control enters, you gain 1 life.

Ajani Goldmane

+1: You gain 2 life.
−1: Put a +1/+1 counter on each creature you control. Those creatures gain vigilance until end of turn.
−6: Create a white Avatar creature token. It has "This creature's power and toughness are each equal to your life total."