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.

Ajani's Pridemate

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

Blood Researcher

Menace (This creature can't be blocked except by two or more creatures.)
Whenever you gain life, put a +1/+1 counter on Blood Researcher.

Gnaw to the Bone

You gain 2 life for each creature card in your graveyard.
Flashback {2}{G} (You may cast this card from your graveyard for its flashback cost. Then exile it.)

Swamp

Ajani, the Greathearted

Creatures you control have vigilance.
+1: You gain 3 life.
−2: Put a +1/+1 counter on each creature you control and a loyalty counter on each other planeswalker you control.

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.

Lone Missionary

When Lone Missionary enters, you gain 4 life.

Exsanguinate

Each opponent loses X life. You gain life equal to the life lost this way.

Bolas's Citadel

You may look at the top card of your library any time.
You may play lands and cast spells from the top of your library. If you cast a spell this way, pay life equal to its mana value rather than pay its mana cost.
{T}, Sacrifice ten nonland permanents: Each opponent loses 10 life.

Nissa, Nature's Artisan

+3: You gain 3 life.
−4: Reveal the top two cards of your library. Put all land cards from among them onto the battlefield and the rest into your hand.
−12: Creatures you control get +5/+5 and gain trample until end of turn.

Garruk, Apex Predator

+1: Destroy another target planeswalker.
+1: Create a 3/3 black Beast creature token with deathtouch.
−3: Destroy target creature. You gain life equal to its toughness.
−8: Target opponent gets an emblem with "Whenever a creature attacks you, it gets +5/+5 and gains trample until end of turn."

Forest

Soul Warden

Whenever another creature enters, you gain 1 life.

Arcane Signet

{T}: Add one mana of any color in your commander's color identity.

Blood Artist

Whenever Blood Artist or another creature dies, target player loses 1 life and you gain 1 life.

Sol Ring

Mana Reflection

If you tap a permanent for mana, it produces twice as much of that mana instead.

Ajani, Valiant Protector

+2: Put two +1/+1 counters on up to one target creature.
+1: Reveal cards from the top of your library until you reveal a creature card. Put that card into your hand and the rest on the bottom of your library in a random order.
−11: Put X +1/+1 counters on target creature, where X is your life total. That creature gains trample until end of turn.

Ob Nixilis of the Black Oath

+2: Each opponent loses 1 life. You gain life equal to the life lost this way.
−2: Create a 5/5 black Demon creature token with flying. You lose 2 life.
−8: You get an emblem with "{1}{B}, Sacrifice a creature: You gain X life and draw X cards, where X is the sacrificed creature's power."
Ob Nixilis of the Black Oath can be your commander.

Soul's Attendant

Whenever another creature enters, you may gain 1 life.

Feed the Clan

You gain 5 life.
Ferocious — You gain 10 life instead if you control a creature with power 4 or greater.

Jungle Hollow

This land enters tapped.
When this land enters, you gain 1 life.
{T}: Add {B} or {G}.

Life Goes On

You gain 4 life. If a creature died this turn, you gain 8 life instead.

Heliod, Sun-Crowned

Indestructible
As long as your devotion to white is less than five, Heliod isn't a creature.
Whenever you gain life, put a +1/+1 counter on target creature or enchantment you control.
{1}{W}: Another target creature gains lifelink until end of turn.

Ajani's Welcome

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

Ajani's Sunstriker

Lifelink (Damage dealt by this creature also causes you to gain that much life.)