Consider

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

Omniscience

You may cast spells from your hand without paying their mana costs.

Decanter of Endless Water

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

Storm-Kiln Artist

Storm-Kiln Artist gets +1/+0 for each artifact you control.
Magecraft — Whenever you cast or copy an instant or sorcery spell, create a Treasure token.

Talrand, Sky Summoner

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

Command Tower

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

Deadeye Navigator

Soulbond (You may pair this creature with another unpaired creature when either enters the battlefield. They remain paired for as long as you control both of them.)
As long as Deadeye Navigator is paired with another creature, each of those creatures has "{1}{U}: Exile this creature, then return it to the battlefield under your control."

Wanderwine Prophets

Champion a Merfolk (When this enters the battlefield, sacrifice it unless you exile another Merfolk you control. When this leaves the battlefield, that card returns to the battlefield.)
Whenever Wanderwine Prophets deals combat damage to a player, you may sacrifice a Merfolk. If you do, take an extra turn after this one.

Ghostly Flicker

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

Prologue to Phyresis

Each opponent gets a poison counter.
Draw a card.

Fiery Inscription

When Fiery Inscription enters the battlefield, the Ring tempts you.
Whenever you cast an instant or sorcery spell, Fiery Inscription deals 2 damage to each opponent.

Curiosity

Enchant creature
Whenever enchanted creature deals damage to an opponent, you may draw a card.

Mountain

Galazeth Prismari

Flying
When Galazeth Prismari enters the battlefield, create a Treasure token.
Artifacts you control have "{T}: Add one mana of any color. Spend this mana only to cast an instant or sorcery spell."

Radiant Performer

Flash
When Radiant Performer enters the battlefield, if you cast it from your hand, choose target spell or ability that targets only a single permanent or player. Copy that spell or ability for each other permanent or player the spell or ability could target. Each copy targets a different one of those permanents and players.

Niv-Mizzet, the Firemind

Flying
Whenever you draw a card, Niv-Mizzet, the Firemind deals 1 damage to any target.
{T}: Draw a card.

Island

Spellbook

Sky Diamond

Sky Diamond enters the battlefield tapped.
{T}: Add {U}.

Guttersnipe

Whenever you cast an instant or sorcery spell, Guttersnipe deals 2 damage to each opponent.

Shipwreck Dowser

Prowess (Whenever you cast a noncreature spell, this creature gets +1/+1 until end of turn.)
When Shipwreck Dowser enters the battlefield, return target instant or sorcery card from your graveyard to your hand.

Nivix Guildmage

{1}{U}{R}: Draw a card, then discard a card.
{2}{U}{R}: Copy target instant or sorcery spell you control. You may choose new targets for the copy.

Mystical Tutor

Search your library for an instant or sorcery card, reveal it, then shuffle and put that card on top.

Izzet Locket

{T}: Add {U} or {R}.
{U/R}{U/R}{U/R}{U/R}, {T}, Sacrifice Izzet Locket: Draw two cards.

Goblin Electromancer

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

Archmage Emeritus

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

Sage of the Falls

Whenever Sage of the Falls or another non-Human creature enters the battlefield under your control, you may draw a card. If you do, discard a card.

Narset's Reversal

Copy target instant or sorcery spell, then return it to its owner's hand. You may choose new targets for the copy.

Ponder

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

Izzet Signet

Izzet Chronarch

When Izzet Chronarch enters the battlefield, return target instant or sorcery card from your graveyard to your hand.

Grapeshot

Grapeshot deals 1 damage to any target.
Storm (When you cast this spell, copy it for each spell cast before it this turn. You may choose new targets for the copies.)

Molten Echoes

As Molten Echoes enters the battlefield, choose a creature type.
Whenever a nontoken creature of the chosen type enters the battlefield under your control, create a token that's a copy of that creature. That token gains haste. Exile it at the beginning of the next end step.

Mirror Sheen

{1}{U/R}{U/R}: Copy target instant or sorcery spell that targets you. You may choose new targets for the copy.

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.)

Reliquary Tower

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

Arcane Signet

Thousand-Year Storm

Whenever you cast an instant or sorcery spell, copy it for each other instant and sorcery spell you've cast before it this turn. You may choose new targets for the copies.

Niv-Mizzet, Parun

This spell can't be countered.
Flying
Whenever you draw a card, Niv-Mizzet, Parun deals 1 damage to any target.
Whenever a player casts an instant or sorcery spell, you draw a card.

Frantic Search

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

Witty Roastmaster

Alliance — Whenever another creature enters the battlefield under your control, Witty Roastmaster deals 1 damage to each opponent.

Counterspell

Lightning Bolt

Lightning Bolt deals 3 damage to any target.

Confiscate

Enchant permanent
You control enchanted permanent.

Followed Footsteps

Enchant creature
At the beginning of your upkeep, create a token that's a copy of enchanted creature.

Laboratory Maniac

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

Dualcaster Mage

Flash
When Dualcaster Mage enters the battlefield, copy target instant or sorcery spell. You may choose new targets for the copy.

The Locust God

Flying
Whenever you draw a card, create a 1/1 blue and red Insect creature token with flying and haste.
{2}{U}{R}: Draw a card, then discard a card.
When The Locust God dies, return it to its owner's hand at the beginning of the next end step.

Temporal Manipulation

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, Sky Dreamer and Drakes you control each get +X/+X until end of turn, where X is the number of cards in your hand.

Deep Analysis

Target player draws two cards.
Flashback—{1}{U}, Pay 3 life. (You may cast this card from your graveyard for its flashback cost. Then exile it.)

Essence Flux

Exile target creature you control, then return that card to the battlefield under its owner's control. If it's a Spirit, put a +1/+1 counter on it.

Storm King's Thunder

When you next cast an instant or sorcery spell this turn, copy that spell X times. You may choose new targets for the copies.

Xorn

If you would create one or more Treasure tokens, instead create those tokens plus an additional Treasure token.

Talisman of Creativity

{T}: Add {C}.
{T}: Add {U} or {R}. Talisman of Creativity deals 1 damage to you.

Faithless Looting

Draw two cards, then discard two cards.
Flashback {2}{R} (You may cast this card from your graveyard for its flashback cost. Then exile it.)

Wavebreak Hippocamp

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

Thought Vessel

Quicken

The next sorcery spell you cast this turn can be cast as though it had flash. (It can be cast any time you could cast an instant.)
Draw a card.

Sol Ring

Expedite

Target creature gains haste until end of turn.
Draw a card.

Commander's Sphere

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

Lightning Crafter

Champion a Goblin or Shaman (When this enters the battlefield, sacrifice it unless you exile another Goblin or Shaman you control. When this leaves the battlefield, that card returns to the battlefield.)
{T}: Lightning Crafter deals 3 damage to any target.

Ral Zarek

+1: Tap target permanent, then untap another target permanent.
−2: Ral Zarek deals 3 damage to any target.
−7: Flip five coins. Take an extra turn after this one for each coin that comes up heads.

Arcane Melee

Instant and sorcery spells cost {2} less to cast.

Flame of Anor

Choose one. If you control a Wizard as you cast this spell, you may choose two instead.
• Target player draws two cards.
• Destroy target artifact.
• Flame of Anor deals 5 damage to target creature.

Brainstorm

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

Dramatic Reversal

Untap all nonland permanents you control.

Jori En, Ruin Diver

Whenever you cast your second spell each turn, draw a card.

Isochron Scepter

Imprint — When Isochron Scepter enters the battlefield, you may exile an instant card with mana value 2 or less from your hand.
{2}, {T}: You may copy the exiled card. If you do, you may cast the copy without paying its mana cost.

Fire Diamond

Fire Diamond enters the battlefield tapped.
{T}: Add {R}.

Turnabout

Choose artifact, creature, or land. Tap all untapped permanents of the chosen type target player controls, or untap all tapped permanents of that type that player controls.