Leonin Vanguard

At the beginning of combat on your turn, if you control three or more creatures, this creature gets +1/+1 until end of turn and you gain 1 life.

Cliffhaven Kitesail

When Cliffhaven Kitesail enters, attach it to target creature you control.
Equipped creature has flying.
Equip {2} ({2}: Attach to target creature you control. Equip only as a sorcery.)

Ajani's Welcome

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

Plains

Soul Warden

Whenever another creature enters, you gain 1 life.

Cleric Class

(Gain the next level as a sorcery to add its ability.)
If you would gain life, you gain that much life plus 1 instead.
{3}{W}: Level 2
Whenever you gain life, put a +1/+1 counter on target creature you control.
{4}{W}: Level 3
When this Class becomes level 3, return target creature card from your graveyard to the battlefield. You gain life equal to that creature's toughness.

Alseid of Life's Bounty

Lifelink
{1}, Sacrifice Alseid of Life's Bounty: Target creature or enchantment you control gains protection from the color of your choice until end of turn.

Angel of Vitality

Flying
If you would gain life, you gain that much life plus 1 instead.
This creature gets +2/+2 as long as you have 25 or more life.

Hallowed Priest

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

Ajani's Pridemate

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

Inspiring Commander

Whenever another creature you control with power 2 or less enters, you gain 1 life and draw a card.