Plains

Light of Promise

Enchant creature
Enchanted creature has "Whenever you gain life, put that many +1/+1 counters on this creature."

Aetherflux Reservoir

Whenever you cast a spell, you gain 1 life for each spell you've cast this turn.
Pay 50 life: Aetherflux Reservoir deals 50 damage to any target.

Pride Guardian

Defender
Whenever Pride Guardian blocks, you gain 3 life.

Spirit Link

Enchant creature (Target a creature as you cast this. This card enters attached to that creature.)
Whenever enchanted creature deals damage, you gain that much life.

Felidar Sovereign

Vigilance (Attacking doesn't cause this creature to tap.)
Lifelink (Damage dealt by this creature also causes you to gain that much life.)
At the beginning of your upkeep, if you have 40 or more life, you win the game.

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.

Ajani's Pridemate

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

Ajani's Welcome

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

Swords to Plowshares

Exile target creature. Its controller gains life equal to its power.

Speaker of the Heavens

Vigilance, lifelink (Attacking doesn't cause this creature to tap. Damage dealt by this creature also causes you to gain that much life.)
{T}: Create a 4/4 white Angel creature token with flying. Activate only if you have at least 7 life more than your starting life total and only as a sorcery.

Fountain of Renewal

At the beginning of your upkeep, you gain 1 life.
{3}, Sacrifice Fountain of Renewal: Draw a card.