Consider

Surveil 1. (Look at the top card of your library. You may put it into your graveyard.)
Draw a card.

Growth Spiral

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

Preordain

Scry 2, then draw a card. (To scry 2, look at the top two cards of your library, then put any number of them on the bottom and the rest on top in any order.)

Explore

You may play an additional land this turn.
Draw a card.

Thought Scour

Target player mills two cards.
Draw a card.

Unsummon

Return target creature to its owner's hand.

Sage's Row Denizen

Whenever another blue creature enters the battlefield under your control, target player mills two cards.

Island

Shielding Plax

({G/U} can be paid with either {G} or {U}.)
Enchant creature
When Shielding Plax enters the battlefield, draw a card.
Enchanted creature can't be the target of spells or abilities your opponents control.

Thornwood Falls

Thornwood Falls enters the battlefield tapped.
When Thornwood Falls enters the battlefield, you gain 1 life.
{T}: Add {G} or {U}.

Vapor Snag

Return target creature to its owner's hand. Its controller loses 1 life.

Jace's Erasure

Whenever you draw a card, you may have target player mill a card.

Ponder

Look at the top three cards of your library, then put them back in any order. You may shuffle.
Draw a card.

Dream Twist

Target player mills three cards.
Flashback {1}{U} (You may cast this card from your graveyard for its flashback cost. Then exile it.)

Tangle

Prevent all combat damage that would be dealt this turn.
Each attacking creature doesn't untap during its controller's next untap step.

Fade Away

For each creature, its controller sacrifices a permanent unless they pay {1}.

Mind Sculpt

Brainstorm

Draw three cards, then put two cards from your hand on top of your library in any order.

Moment's Peace

Prevent all combat damage that would be dealt this turn.
Flashback {2}{G} (You may cast this card from your graveyard for its flashback cost. Then exile it.)

Venture Deeper

Target player mills four cards. (Then exile this card. You may cast the creature later from exile.)

Merfolk Secretkeeper

Merfolk Secretkeeper // Venture Deeper

Turn Aside

Counter target spell that targets a permanent you control.

Memory Sluice

Target player mills four cards.
Conspire (As you cast this spell, you may tap two untapped creatures you control that share a color with it. When you do, copy it and you may choose a new target for the copy.)

Shrieking Drake

Flying
When Shrieking Drake enters the battlefield, return a creature you control to its owner's hand.