Dire Fleet Captain

Whenever Dire Fleet Captain attacks, it gets +1/+1 until end of turn for each other attacking Pirate.

Dire Fleet Poisoner

Flash
Deathtouch
When Dire Fleet Poisoner enters the battlefield, target attacking Pirate you control gets +1/+1 and gains deathtouch until end of turn.

Bloodstained Mire

{T}, Pay 1 life, Sacrifice Bloodstained Mire: Search your library for a Swamp or Mountain card, put it onto the battlefield, then shuffle.

Daring Buccaneer

As an additional cost to cast this spell, reveal a Pirate card from your hand or pay {2}.

Lightning Bolt

Lightning Bolt deals 3 damage to any target.

Swamp

Fathom Fleet Captain

Menace
Whenever Fathom Fleet Captain attacks, if you control another nontoken Pirate, you may pay {2}. If you do, create a 2/2 black Pirate creature token with menace.

Mountain

Ragavan, Nimble Pilferer

Whenever Ragavan, Nimble Pilferer deals combat damage to a player, create a Treasure token and exile the top card of that player's library. Until end of turn, you may cast that card.
Dash {1}{R} (You may cast this spell for its dash cost. If you do, it gains haste, and it's returned from the battlefield to its owner's hand at the beginning of the next end step.)

Pitiless Plunderer

Whenever another creature you control dies, create a Treasure token. (It's an artifact with "{T}, Sacrifice this artifact: Add one mana of any color.")

Forerunner of the Coalition

When Forerunner of the Coalition enters the battlefield, you may search your library for a Pirate card, reveal it, then shuffle and put that card on top.
Whenever another Pirate enters the battlefield under your control, each opponent loses 1 life.

Wily Goblin

When Wily Goblin enters the battlefield, create a Treasure token. (It's an artifact with "{T}, Sacrifice this artifact: Add one mana of any color.")