Consider

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

Twinning Staff

If you would copy a spell one or more times, instead copy it that many times plus an additional time. You may choose new targets for the additional copy.
{7}, {T}: Copy target instant or sorcery spell you control. You may choose new targets for the copy.

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.

Remand

Counter target spell. If that spell is countered this way, put it into its owner's hand instead of into that player's graveyard.
Draw a card.

Reset

Cast this spell only during an opponent's turn after their upkeep step.
Untap all lands you control.

Lightning Bolt

Lightning Bolt deals 3 damage to any target.

Emeritus of Conflict

First strike
Whenever you cast your third spell each turn, this creature becomes prepared. (While it's prepared, you may cast a copy of its spell. Doing so unprepares it.)

Emeritus of Conflict // Lightning Bolt

Unstoppable Plan

At the beginning of your end step, untap all nonland permanents you control.

Brain Freeze

Target player mills three cards.
Storm (When you cast this spell, copy it for each spell cast before it this turn. You may choose new targets for the copies.)

Improvisation Capstone

Exile cards from the top of your library until you exile cards with total mana value 4 or greater. You may cast any number of spells from among them without paying their mana costs.
Paradigm (Then exile this spell. After you first resolve a spell with this name, you may cast a copy of it from exile without paying its mana cost at the beginning of each of your first main phases.)

Deflecting Swat

If you control a commander, you may cast this spell without paying its mana cost.
You may choose new targets for target spell or ability.

High Fae Trickster

Flash (You may cast this spell any time you could cast an instant.)
Flying
You may cast spells as though they had flash.

Reiterate

Buyback {3} (You may pay an additional {3} as you cast this spell. If you do, put this card into your hand as it resolves.)
Copy target instant or sorcery spell. You may choose new targets for the copy.

Sol Ring

Abstract Paintmage

At the beginning of your first main phase, add {U}{R}. Spend this mana only to cast instant and sorcery spells.

Force of Will

You may pay 1 life and exile a blue card from your hand rather than pay this spell's mana cost.
Counter target spell.

Tablet of Discovery

When this artifact enters, mill a card. You may play that card this turn. (To mill a card, put the top card of your library into your graveyard.)
{T}: Add {R}.
{T}: Add {R}{R}. Spend this mana only to cast instant and sorcery spells.

Flow State

Look at the top three cards of your library. Put one of them into your hand and the rest on the bottom of your library in any order. If there is an instant card and a sorcery card in your graveyard, instead put two of them into your hand and the rest on the bottom of your library in any order.

Island

Jeska's Will

Choose one. If you control a commander as you cast this spell, you may choose both instead.
• Add {R} for each card in target opponent's hand.
• Exile the top three cards of your library. You may play them this turn.

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.

Gitaxian Probe

({U/P} can be paid with either {U} or 2 life.)
Look at target player's hand.
Draw a card.

Storm-Kiln Artist

This creature gets +1/+0 for each artifact you control.
Magecraft — Whenever you cast or copy an instant or sorcery spell, create a Treasure token. (It's an artifact with "{T}, Sacrifice this token: Add one mana of any color.")

Chain Lightning

Chain Lightning deals 3 damage to any target. Then that player or that permanent's controller may pay {R}{R}. If the player does, they may copy this spell and may choose a new target for that copy.

Electro, Assaulting Battery

Flying
You don't lose unspent red mana as steps and phases end.
Whenever you cast an instant or sorcery spell, add {R}.
When Electro leaves the battlefield, you may pay {X}. When you do, he deals X damage to target player.

Mountain

Ponder

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

Zaffai and the Tempests

Once during each of your turns, you may cast an instant or sorcery spell from your hand without paying its mana cost.

Command Tower

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

Prismari Charm

Choose one —
• Surveil 2, then draw a card.
• Prismari Charm deals 1 damage to each of one or two targets.
• Return target nonland permanent to its owner's hand.

Archmage Emeritus

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

Mana Geyser

Add {R} for each tapped land your opponents control.

Ancestral Recall

Emeritus of Ideation

Flying, ward {2}
This creature enters prepared.
Whenever this creature attacks, you may exile eight cards from your graveyard. If you do, this creature becomes prepared.

Emeritus of Ideation // Ancestral Recall

Prismari, the Inspiration

Flying
Ward—Pay 5 life.
Instant and sorcery spells you cast have storm. (Whenever you cast an instant or sorcery spell, copy it for each spell cast before it this turn. You may choose new targets for the copies.)

Bolt Bend

This spell costs {3} less to cast if you control a creature with power 4 or greater.
Change the target of target spell or ability with a single target.

Fireball

This spell costs {1} more to cast for each target beyond the first.
Fireball deals X damage divided evenly, rounded down, among any number of targets.

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.)

Talisman of Creativity

{T}: Add {C}.
{T}: Add {U} or {R}. This artifact deals 1 damage to you.

Harnfel, Horn of Bounty

Discard a card: Exile the top two cards of your library. You may play those cards this turn.

Birgi, God of Storytelling

Whenever you cast a spell, add {R}. Until end of turn, you don't lose this mana as steps and phases end.
Creatures you control can boast twice during each of your turns rather than once.