Open the Gates

Search your library for a basic land card or Gate card, reveal it, put it into your hand, then shuffle.

Greenside Watcher

Arboreal Grazer

Reach
When Arboreal Grazer enters, you may put a land card from your hand onto the battlefield tapped.

Eureka Moment

Draw two cards. You may put a land card from your hand onto the battlefield.

Heap Gate

{T}: Add {C}.
{1}, {T}: Add one mana of any color.
{1}, {T}, Tap an untapped Gate you control: Create a Treasure token. (It's an artifact with "{T}, Sacrifice this artifact: Add one mana of any color.")

Sea Gate

Sea Gate enters tapped.
As Sea Gate enters, choose a color other than blue.
{T}: Add {U} or one mana of the chosen color.

Manor Gate

Manor Gate enters tapped.
As Manor Gate enters, choose a color other than green.
{T}: Add {G} or one mana of the chosen color.

Broken Bond

Destroy target artifact or enchantment. You may put a land card from your hand onto the battlefield.

Saruli Gatekeepers

When Saruli Gatekeepers enters, if you control two or more Gates, you gain 7 life.

Growth Spiral

Draw a card. You may put a land card from your hand onto the battlefield.

Basilisk Gate

{T}: Add {C}.
{2}, {T}: Target creature gets +X/+X until end of turn, where X is the number of Gates you control. Activate only as a sorcery.

Simic Guildgate

Simic Guildgate enters tapped.
{T}: Add {G} or {U}.

Gatecreeper Vine

Defender
When Gatecreeper Vine enters, you may search your library for a basic land card or a Gate card, reveal it, put it into your hand, then shuffle.

Opal Lake Gatekeepers

When Opal Lake Gatekeepers enters, if you control two or more Gates, you may draw a card.