Consider

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

Skyskipper Duo

Flying
When this creature enters, exile up to one other target creature you control. Return it to the battlefield under its owner's control at the beginning of the next end step.

Shore Up

Target creature you control gets +1/+1 and gains hexproof until end of turn. Untap it. (It can't be the target of spells or abilities your opponents control.)

Scry 1. (Look at the top card of your library. You may put that card on the bottom.)
Draw a card.

Sandstone Bridge

This land enters tapped.
When this land enters, target creature gets +1/+1 and gains vigilance until end of turn.
{T}: Add {W}.

Center Soul

Target creature you control gains protection from the color of your choice until end of turn.
Rebound (If you cast this spell from your hand, exile it as it resolves. At the beginning of your next upkeep, you may cast this card from exile without paying its mana cost.)

Oasis Gardener

When this creature enters, you gain 2 life.
{T}: Add one mana of any color.

Idyllic Beachfront

({T}: Add {W} or {U}.)
This land enters tapped.

Enlightened Ascetic

When this creature enters, you may destroy target enchantment.

Thought Vessel

You have no maximum hand size.
{T}: Add {C}.

Intrepid Rabbit

Offspring {1} (You may pay an additional {1} as you cast this spell. If you do, when this creature enters, create a 1/1 token copy of it.)
When this creature enters, target creature you control gets +1/+1 until end of turn.

Wall of Omens

Defender
When this creature enters, draw a card.

Holy Cow

Flash
Flying
When this creature enters, you gain 2 life and scry 1. (Look at the top card of your library. You may put that card on the bottom.)

Candlekeep Sage

Commander creatures you own have "When this creature enters or leaves the battlefield, draw a card."

Lonely Arroyo

This land enters tapped.
When this land enters, it deals 1 damage to target opponent.
{T}: Add {W} or {U}.

Archaeomancer

When this creature enters, return target instant or sorcery card from your graveyard to your hand.

Mnemonic Wall

Defender
When this creature enters, you may return target instant or sorcery card from your graveyard to your hand.

Pileated Provisioner

Flying
When this creature enters, put a +1/+1 counter on target creature you control without flying.

Stagecoach Security

When this creature enters, creatures you control get +1/+1 and gain vigilance until end of turn.
Plot {3}{W} (You may pay {3}{W} and exile this card from your hand. Cast it as a sorcery on a later turn without paying its mana cost. Plot only as a sorcery.)

Contact Other Plane

Roll a d20.
1—9 | Draw two cards.
10—19 | Scry 2, then draw two cards.
20 | Scry 3, then draw three cards.

Plains

Spirited Companion

Azorius Locket

{T}: Add {W} or {U}.
{W/U}{W/U}{W/U}{W/U}, {T}, Sacrifice this artifact: Draw two cards.

Opal Palace

{T}: Add {C}.
{1}, {T}: Add one mana of any color in your commander's color identity. If you spend this mana to cast your commander, it enters with a number of additional +1/+1 counters on it equal to the number of times it's been cast from the command zone this game.

Unwind

Counter target noncreature spell. Untap up to three lands.

Acrobatic Maneuver

Exile target creature you control, then return that card to the battlefield under its owner's control.
Draw a card.

Prophetic Prism

When this artifact enters, draw a card.
{1}, {T}: Add one mana of any color.

Scouting Hawk

Flying
Keen Sight — When this creature enters, if an opponent controls more lands than you, search your library for a basic Plains card, put it onto the battlefield tapped, then shuffle.

The Fair Basilica

This land enters tapped.
{T}: Add {W}.
{1}{W}, {T}, Sacrifice this land: Draw a card.

Rosecot Knight

Vigilance
When this creature enters, look at the top six cards of your library. You may reveal an artifact or enchantment card from among them and put it into your hand. Put the rest on the bottom of your library in a random order. If you didn't put a card into your hand this way, put a +1/+1 counter on this creature.

Azorius Signet

Arcane Signet

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

Essence Scatter

Nagging Thoughts

Look at the top two cards of your library. Put one of them into your hand and the other into your graveyard.
Madness {1}{U} (If you discard this card, discard it into exile. When you do, cast it for its madness cost or put it into your graveyard.)

Inspiring Overseer

Flying
When this creature enters, you gain 1 life and draw a card.

Aarakocra Sneak

Flying
When this creature enters, you take the initiative.

Logic Knot

Delve (Each card you exile from your graveyard while casting this spell pays for {1}.)
Counter target spell unless its controller pays {X}.

Arashin Cleric

When this creature enters, you gain 3 life.

The Surgical Bay

This land enters tapped.
{T}: Add {U}.
{1}{U}, {T}, Sacrifice this land: Draw a card.

Command Tower

Evolving Wilds

{T}, Sacrifice this land: Search your library for a basic land card, put it onto the battlefield tapped, then shuffle.

Sky Diamond

This artifact enters tapped.
{T}: Add {U}.

Whisk Away

Put target attacking or blocking creature on top of its owner's library.

Take the Fall

Target creature gets -1/-0 until end of turn. It gets -4/-0 until end of turn instead if you control an outlaw. (Assassins, Mercenaries, Pirates, Rogues, and Warlocks are outlaws.)
Draw a card.

Take Up the Shield

Put a +1/+1 counter on target creature. It gains lifelink and indestructible until end of turn. (Damage and effects that say "destroy" don't destroy it.)

Rescue the Foal

Exile target creature you control, then return that card to the battlefield under its owner's control. (Then exile this card. You may cast the creature later from exile.)

Pegasus Guardian

Flying
At the beginning of your end step, if a permanent you controlled left the battlefield this turn, create a 1/1 white Pegasus creature token with flying.

Pegasus Guardian // Rescue the Foal

Momentary Blink

Exile target creature you control, then return it to the battlefield under its owner's control.
Flashback {3}{U} (You may cast this card from your graveyard for its flashback cost. Then exile it.)

Seize the Secrets

This spell costs {1} less to cast if you've committed a crime this turn. (Targeting opponents, anything they control, and/or cards in their graveyards is a crime.)
Draw two cards.

Harrier Strix

Flying
When this creature enters, tap target permanent.
{2}{U}: Draw a card, then discard a card.

Claustrophobia

Enchant creature
When this Aura enters, tap enchanted creature.
Enchanted creature doesn't untap during its controller's untap step.

Mystic Sanctuary

({T}: Add {U}.)
This land enters tapped unless you control three or more other Islands.
When this land enters untapped, you may put target instant or sorcery card from your graveyard on top of your library.

Write into Being

Look at the top two cards of your library. Manifest one of those cards, then put the other on the top or bottom of your library. (To manifest a card, put it onto the battlefield face down as a 2/2 creature. Turn it face up any time for its mana cost if it's a creature card.)

Inspired Inventor

When this creature enters, choose one —
• You get {E}{E}{E} (three energy counters).
• Put a +1/+1 counter on target creature.
• Create a 1/1 colorless Servo artifact creature token.

Dragonborn Looter

{1}, {T}: Draw a card, then discard a card.

Island

Flaming Fist Officer

Whenever another creature you control leaves the battlefield, put a +1/+1 counter on this creature.

Marble Diamond

This artifact enters tapped.
{T}: Add {W}.

Peerless Ropemaster

When this creature enters, return up to one target tapped creature to its owner's hand.

Minamo Scrollkeeper

Defender
Your maximum hand size is increased by one.

Getting

Unable to Scream

Enchant creature
Enchanted creature loses all abilities and is a Toy artifact creature with base power and toughness 0/2 in addition to its other types.
As long as enchanted creature is face down, it can't be turned face up.

Aerie Auxiliary

Flying
When this creature enters, support 2. (Put a +1/+1 counter on each of up to two other target creatures.)

Tyr's Blessing

Target creature gains indestructible until end of turn. (Then exile this card. You may cast the creature later from exile.)

Blessed Hippogriff

Flying
Whenever this creature attacks, target attacking creature without flying gains flying until end of turn.

Blessed Hippogriff // Tyr's Blessing

Dream Fracture

Counter target spell. Its controller draws a card.
Draw a card.

Ephemerate

Exile target creature you control, then return it to the battlefield under its owner's control.
Rebound (If you cast this spell from your hand, exile it as it resolves. At the beginning of your next upkeep, you may cast this card from exile without paying its mana cost.)

Bulwark Giant

When this creature enters, you gain 5 life.

Winter Eladrin

Gust of Wind — When this creature enters, return up to one other target creature to its owner's hand.

Phantom Interference

Spree (Choose one or more additional costs.)
+ {3} — Create a 2/2 white Spirit creature token with flying.
+ {1} — Counter target spell unless its controller pays {2}.

Blur

Zulaport Duelist

Flash
When this creature enters, up to one target creature gets -2/-0 until end of turn. Its controller mills two cards. (They put the top two cards of their library into their graveyard.)

Capsizing Wave

Return target creature to its owner's hand. (Then exile this card. You may cast the creature later from exile.)

Sword Coast Serpent

This creature can't be blocked as long as you've cast a noncreature spell this turn.

Sword Coast Serpent // Capsizing Wave

Ghostly Flicker

Exile two target artifacts, creatures, and/or lands you control, then return those cards to the battlefield under your control.

Psychic Impetus

Enchant creature
Enchanted creature gets +2/+2 and is goaded. (It attacks each combat if able and attacks a player other than you if able.)
Whenever enchanted creature attacks, you scry 2.

Serum Visionary

When this creature enters, draw a card, then scry 2.

Kill Shot

Snap

Return target creature to its owner's hand. Untap up to two lands.

Sand Augury

Scry 1, then draw a card. (Then exile this card. You may cast the creature later from exile.)

Young Blue Dragon

Young Blue Dragon // Sand Augury

Goliath Paladin

Vigilance
When this creature enters, you take the initiative.

Fountainport Bell

When this artifact enters, you may search your library for a basic land card, reveal it, then shuffle and put that card on top.
{1}, Sacrifice this artifact: Draw a card.

Bellowing Crier

When this creature enters, draw a card, then discard a card.

Roving Harper

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.)

Geyser Drake

Flying
During turns other than yours, spells you cast cost {1} less to cast.

Sterling Supplier

Flying
When this creature enters, put a +1/+1 counter on another target creature you control.

Cloudshift

Exile target creature you control, then return that card to the battlefield under your control.

Decanter of Endless Water

You have no maximum hand size.
{T}: Add one mana of any color.

Lifecreed Duo

Flying
Whenever another creature you control enters, you gain 1 life.

Oji, the Exquisite Blade

When Oji enters, you gain 2 life and scry 2.
Whenever you cast your second spell each turn, exile up to one target creature you control, then return it to the battlefield under its owner's control.

Oceanus Dragon

Flying
When this creature enters, tap target creature an opponent controls. Goad it. (Until your next turn, that creature attacks each combat if able and attacks a player other than you if able.)

Run Away Together

Choose two target creatures controlled by different players. Return those creatures to their owners' hands.

Dog Umbra

Flash
Enchant creature
As long as another player controls enchanted creature, it can't attack or block. Otherwise, this Aura has umbra armor. (If enchanted creature would be destroyed, instead remove all damage from it and destroy this Aura.)

Prosperous Pirates

When this creature enters, create two Treasure tokens. (They're artifacts with "{T}, Sacrifice this token: Add one mana of any color.")

Commander's Sphere

{T}: Add one mana of any color in your commander's color identity.
Sacrifice this artifact: Draw a card.

Negate

Cloud of Faeries

Flying
When this creature enters, untap up to two lands.
Cycling {2} ({2}, Discard this card: Draw a card.)