Consider

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

Curiosity Crafter

Flying
You have no maximum hand size.
Whenever a creature token you control deals combat damage to a player, draw a card.

Murmuring Mystic

Whenever you cast an instant or sorcery spell, create a 1/1 blue Bird Illusion creature token with flying.

Hullbreaker Horror

Flash
This spell can't be countered.
Whenever you cast a spell, choose up to one —
• Return target spell you don't control to its owner's hand.
• Return target nonland permanent to its owner's hand.

Haughty Djinn

Flying
Haughty Djinn's power is equal to the number of instant and sorcery cards in your graveyard.
Instant and sorcery spells you cast cost {1} less to cast.

Laboratory Maniac

If you would draw a card while your library has no cards in it, you win the game instead.

Aetherize

Return all attacking creatures to their owner's hand.

Ponder

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

Counterspell

Island

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

Riptide Laboratory

{T}: Add {C}.
{1}{U}, {T}: Return target Wizard you control to its owner's hand.

High Tide

Until end of turn, whenever a player taps an Island for mana, that player adds an additional {U}.

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.

Octavia, Living Thesis

This spell costs {8} less to cast if you have eight or more instant and/or sorcery cards in your graveyard.
Ward {8}
Magecraft — Whenever you cast or copy an instant or sorcery spell, target creature has base power and toughness 8/8 until end of turn.

Favorable Winds

Creatures you control with flying get +1/+1.

Shark Typhoon

Whenever you cast a noncreature spell, create an X/X blue Shark creature token with flying, where X is that spell's mana value.
Cycling {X}{1}{U} ({X}{1}{U}, Discard this card: Draw a card.)
When you cycle this card, create an X/X blue Shark creature token with flying.

Curse of the Swine

Exile X target creatures. For each creature exiled this way, its controller creates a 2/2 green Boar creature token.

Disallow

Counter target spell, activated ability, or triggered ability. (Mana abilities can't be targeted.)

Brainstorm

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

Extraplanar Lens

Imprint — When this artifact enters, you may exile target land you control.
Whenever a land with the same name as the exiled card is tapped for mana, its controller adds one mana of any type that land produced.

Final Iteration

Flying
Wizards you control get +2/+1 and have flying.
Whenever you cast an instant or sorcery spell, create a 1/1 blue Human Wizard creature token.

Docent of Perfection

Flying
Whenever you cast an instant or sorcery spell, create a 1/1 blue Human Wizard creature token. Then if you control three or more Wizards, transform this creature.

Docent of Perfection // Final Iteration

Mocking Sprite

Flying
Instant and sorcery spells you cast cost {1} less to cast.

Archaeomancer

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

Eluge, the Shoreless Sea

Eluge's power and toughness are each equal to the number of Islands you control.
Whenever Eluge enters or attacks, put a flood counter on target land. It's an Island in addition to its other types for as long as it has a flood counter on it.
The first instant or sorcery spell you cast each turn costs {U} (or {1}) less to cast for each land you control with a flood counter on it.

Harbinger of the Seas

Pongify

Destroy target creature. It can't be regenerated. Its controller creates a 3/3 green Ape creature token.

Bident of Thassa

Whenever a creature you control deals combat damage to a player, you may draw a card.
{1}{U}, {T}: Creatures your opponents control attack this turn if able.

Guile

This creature can't be blocked except by three or more creatures.
If a spell or ability you control would counter a spell, instead exile that spell and you may play that card without paying its mana cost.
When Guile is put into a graveyard from anywhere, shuffle it into its owner's library.

An Offer You Can't Refuse

Counter target noncreature spell. Its controller creates two Treasure tokens. (They're artifacts with "{T}, Sacrifice this token: Add one mana of any color.")

Geyser Drake

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

Negate

Think Twice

Draw a card.
Flashback {2}{U} (You may cast this card from your graveyard for its flashback cost. Then exile it.)

Fact or Fiction

Reveal the top five cards of your library. An opponent separates those cards into two piles. Put one pile into your hand and the other into your graveyard.

Reconnaissance Mission

Whenever a creature you control deals combat damage to a player, you may draw a card.
Cycling {2} ({2}, Discard this card: Draw a card.)

Thunderclap Drake

Flying
Instant and sorcery spells you cast cost {1} less to cast.
{2}{U}, Sacrifice this creature: When you next cast an instant or sorcery spell this turn, copy it for each time you've cast your commander from the command zone this game. You may choose new targets for the copies.

Frantic Search

Draw two cards, then discard two cards. Untap up to three lands.

Remote Isle

This land enters tapped.
{T}: Add {U}.
Cycling {2} ({2}, Discard this card: Draw a card.)

Glen Elendra Archmage

Flying
{U}, Sacrifice this creature: Counter target noncreature spell.
Persist (When this creature dies, if it had no -1/-1 counters on it, return it to the battlefield under its owner's control with a -1/-1 counter on it.)

Jin-Gitaxias, Progress Tyrant

Whenever you cast an artifact, instant, or sorcery spell, copy that spell. You may choose new targets for the copy. This ability triggers only once each turn. (A copy of a permanent spell becomes a token.)
Whenever an opponent casts an artifact, instant, or sorcery spell, counter that spell. This ability triggers only once each turn.

Spark Double

You may have this creature enter as a copy of a creature or planeswalker you control, except it enters with an additional +1/+1 counter on it if it's a creature, it enters with an additional loyalty counter on it if it's a planeswalker, and it isn't legendary.

Mind Stone

{T}: Add {C}.
{1}, {T}, Sacrifice this artifact: Draw a card.

Impulse

Look at the top four cards of your library. Put one of them into your hand and the rest on the bottom of your library in any order.

Alandra, Sky Dreamer

Whenever you draw your second card each turn, create a 2/2 blue Drake creature token with flying.
Whenever you draw your fifth card each turn, Alandra and Drakes you control each get +X/+X until end of turn, where X is the number of cards in your hand.

Resculpt

Exile target artifact or creature. Its controller creates a 4/4 blue and red Elemental creature token.

Snap

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

Baral, Chief of Compliance

Instant and sorcery spells you cast cost {1} less to cast.
Whenever a spell or ability you control counters a spell, you may draw a card. If you do, discard a card.

Cryptic Command

Choose two —
• Counter target spell.
• Return target permanent to its owner's hand.
• Tap all creatures your opponents control.
• Draw a card.

Chart a Course

Draw two cards. Then discard a card unless you attacked this turn.

Winged Words

This spell costs {1} less to cast if you control a creature with flying.
Draw two cards.

Sapphire Medallion

Blue spells you cast cost {1} less to cast.

Rise from the Tides

Create a tapped 2/2 black Zombie creature token for each instant and sorcery card in your graveyard.

Lonely Sandbar

This land enters tapped.
{T}: Add {U}.
Cycling {U} ({U}, Discard this card: Draw a card.)

Sol Ring

Wizards of Thay

Myriad (Whenever this creature attacks, for each opponent other than defending player, you may create a token copy that's tapped and attacking that player or a planeswalker they control. Exile the tokens at end of combat.)
Instant and sorcery spells you cast cost {1} less to cast.
You may cast sorcery spells as though they had flash.

Three Steps Ahead

Spree (Choose one or more additional costs.)
+ {1}{U} — Counter target spell.
+ {3} — Create a token that's a copy of target artifact or creature you control.
+ {2} — Draw two cards, then discard a card.

Spectral Deluge

Return each creature your opponents control with toughness X or less to its owner's hand, where X is the number of Islands you control.
Foretell {1}{U}{U} (During your turn, you may pay {2} and exile this card from your hand face down. Cast it on a later turn for its foretell cost.)

Spellseeker

When this creature enters, you may search your library for an instant or sorcery card with mana value 2 or less, reveal it, put it into your hand, then shuffle.

Reliquary Tower

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

Unsummon

Return target creature to its owner's hand.

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.)

Archmage Emeritus

Magecraft — Whenever you cast or copy an instant or sorcery spell, draw a card.

Windfall

Each player discards their hand, then draws cards equal to the greatest number of cards a player discarded this way.

Archmage of Runes

Instant and sorcery spells you cast cost {1} less to cast.
Whenever you cast an instant or sorcery spell, draw a card.

Snapcaster Mage

Flash
When this creature enters, target instant or sorcery card in your graveyard gains flashback until end of turn. The flashback cost is equal to its mana cost. (You may cast that card from your graveyard for its flashback cost. Then exile it.)

Flood of Recollection

Return target instant or sorcery card from your graveyard to your hand. Exile Flood of Recollection.

Talrand, Sky Summoner

Whenever you cast an instant or sorcery spell, create a 2/2 blue Drake creature token with flying.

Enduring Curiosity

Flash
Whenever a creature you control deals combat damage to a player, draw a card.
When Enduring Curiosity dies, if it was a creature, return it to the battlefield under its owner's control. It's an enchantment. (It's not a creature.)

Wavebreak Hippocamp

Whenever you cast your first spell during each opponent's turn, draw a card.

Reality Shift

Exile target creature. Its controller manifests the top card of their library. (That player puts the top card of their library onto the battlefield face down as a 2/2 creature. If it's a creature card, it can be turned face up any time for its mana cost.)