Farseek

Search your library for a Plains, Island, Swamp, or Mountain card, put it onto the battlefield tapped, then shuffle.

Essence Warden

Whenever another creature enters, you gain 1 life.

Veinwitch Coven

Menace
Whenever you gain life, you may pay {B}. If you do, return target creature card from your graveyard to your hand.

Soul Warden

Soul's Attendant

Whenever another creature enters, you may gain 1 life.

Birds of Paradise

Ikra Shidiqi, the Usurper

Menace
Whenever a creature you control deals combat damage to a player, you gain life equal to that creature's toughness.
Partner (You can have two commanders if both have partner.)

Nashi, Moon Sage's Scion

Ninjutsu {3}{B} ({3}{B}, Return an unblocked attacker you control to hand: Put this card onto the battlefield from your hand tapped and attacking.)
Whenever Nashi, Moon Sage's Scion deals combat damage to a player, exile the top card of each player's library. Until end of turn, you may play one of those cards. If you cast a spell this way, pay life equal to its mana value rather than paying its mana cost.

Vito, Thorn of the Dusk Rose

Whenever you gain life, target opponent loses that much life.
{3}{B}{B}: Creatures you control gain lifelink until end of turn.

Trelasarra, Moon Dancer

Whenever you gain life, put a +1/+1 counter on Trelasarra, Moon Dancer and scry 1. (Look at the top card of your library. You may put that card on the bottom.)

Well of Lost Dreams

Whenever you gain life, you may pay {X}, where X is less than or equal to the amount of life you gained. If you do, draw X cards.

Kodama's Reach

Search your library for up to two basic land cards, reveal those cards, put one onto the battlefield tapped and the other into your hand, then shuffle.

Rampant Growth

Search your library for a basic land card, put that card onto the battlefield tapped, then shuffle.

Lisette, Dean of the Root

Whenever you gain life, you may pay {1}. If you do, put a +1/+1 counter on each creature you control and those creatures gain trample until end of turn.

Valentin, Dean of the Vein

Menace, lifelink
If a nontoken creature an opponent controls would die, exile it instead. When you do, you may pay {2}. If you do, create a 1/1 black and green Pest creature token with "When this creature dies, you gain 1 life."

Valentin, Dean of the Vein // Lisette, Dean of the Root

Voice of the Blessed

Whenever you gain life, put a +1/+1 counter on Voice of the Blessed.
As long as Voice of the Blessed has four or more +1/+1 counters on it, it has flying and vigilance.
As long as Voice of the Blessed has ten or more +1/+1 counters on it, it has indestructible.

Archangel of Thune

Flying
Lifelink (Damage dealt by this creature also causes you to gain that much life.)
Whenever you gain life, put a +1/+1 counter on each creature you control.

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.

Orzhov Signet

Tymna the Weaver

Lifelink
At the beginning of each of your postcombat main phases, you may pay X life, where X is the number of opponents that were dealt combat damage this turn. If you do, draw X cards.
Partner (You can have two commanders if both have partner.)

Blossoming Bogbeast

Whenever Blossoming Bogbeast attacks, you gain 2 life. Then creatures you control gain trample and get +X/+X until end of turn, where X is the amount of life you gained this turn.

Sol Ring

Selesnya Signet

Mortality Spear

This spell costs {2} less to cast if you gained life this turn.
Destroy target nonland permanent.

Lathiel, the Bounteous Dawn

Lifelink
At the beginning of each end step, if you gained life this turn, distribute up to that many +1/+1 counters among any number of other target creatures.

Cultivate

Arcane Signet

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

Kambal, Consul of Allocation

Whenever an opponent casts a noncreature spell, that player loses 2 life and you gain 2 life.