Consider

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

Arcane Signet

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

Skyshroud Claim

Search your library for up to two Forest cards, put them onto the battlefield, then shuffle.

Stella Lee, Wild Card

Whenever you cast your second spell each turn, exile the top card of your library. Until the end of your next turn, you may play that card.
{T}: Copy target instant or sorcery spell you control. You may choose new targets for the copy. Activate only if you've cast three or more spells this turn.

Desperate Ritual

Add {R}{R}{R}.
Splice onto Arcane {1}{R} (As you cast an Arcane spell, you may reveal this card from your hand and pay its splice cost. If you do, add this card's effects to that spell.)

Mana Geyser

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

Darksteel Plate

Indestructible
Equipped creature has indestructible.
Equip {2}

Heartbeat of Spring

Whenever a player taps a land for mana, that player adds one mana of any type that land produced.

Mana Drain

Counter target spell. At the beginning of your next main phase, add an amount of {C} equal to that spell's mana value.

Firemind Vessel

This artifact enters tapped.
{T}: Add two mana of different colors.

Talisman of Curiosity

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

Cultivate

Search your library for up to two basic land cards, reveal those cards, put one onto the battlefield tapped and the other into your hand, then shuffle.

Cerulean Wisps

Target creature becomes blue until end of turn. Untap that creature.
Draw a card.

Auroral Procession

Return target card from your graveyard to your hand.

Journey to the Oracle

You may put any number of land cards from your hand onto the battlefield. Then if you control eight or more lands, you may discard a card. If you do, return Journey to the Oracle to its owner's hand.

Jadzi, Oracle of Arcavios

Discard a card: Return Jadzi to its owner's hand.
Magecraft — Whenever you cast or copy an instant or sorcery spell, reveal the top card of your library. If it's a nonland card, you may cast it by paying {1} rather than paying its mana cost. If it's a land card, put it onto the battlefield.

Jadzi, Oracle of Arcavios // Journey to the Oracle

Chromatic Orrery

You may spend mana as though it were mana of any color.
{T}: Add {C}{C}{C}{C}{C}.
{5}, {T}: Draw a card for each color among permanents you control.

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.

Taiga

Strike It Rich

Create a Treasure token. (It's an artifact with "{T}, Sacrifice this token: Add one mana of any color.")
Flashback {2}{R} (You may cast this card from your graveyard for its flashback cost. Then exile it.)

Rampant Growth

Search your library for a basic land card, put that card onto the battlefield tapped, then shuffle.

Thought Scour

Target player mills two cards.
Draw a card.

Mana Flare

Aqueous Form

Enchant creature
Enchanted creature can't be blocked.
Whenever enchanted creature attacks, scry 1. (Look at the top card of your library. You may put that card on the bottom.)

Thundering Falls

({T}: Add {U} or {R}.)
This land enters tapped.
When this land enters, surveil 1. (Look at the top card of your library. You may put it into your graveyard.)

Disciple of the Ring

{1}, Exile an instant or sorcery card from your graveyard: Choose one —
• Counter target noncreature spell unless its controller pays {2}.
• This creature gets +1/+1 until end of turn.
• Tap target creature.
• Untap target creature.

Viewpoint Synchronization

Freerunning {2}{G} (You may cast this spell for its freerunning cost if you dealt combat damage to a player this turn with an Assassin or commander.)
Search your library for up to three basic land cards and reveal them. Put two of them onto the battlefield tapped and the other into your hand, then shuffle.

Sphinx of Forgotten Lore

Flash (You may cast this spell any time you could cast an instant.)
Flying
Whenever this creature attacks, target instant or sorcery card in your graveyard gains flashback until end of turn. The flashback cost is equal to that card's mana cost. (You may cast that card from your graveyard for its flashback cost. Then exile it.)

Talrand, Sky Summoner

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

Overabundance

Whenever a player taps a land for mana, that player adds one mana of any type that land produced, and this enchantment deals 1 damage to the player.

Expedite

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

Storm, Force of Nature

Flying, vigilance
Ceaseless Tempest — Whenever Storm deals combat damage to a player, the next instant or sorcery spell you cast this turn has storm. (When you cast it, copy it for each spell cast before it this turn. You may choose new targets for the copies.)

Breeding Pool

({T}: Add {G} or {U}.)
As this land enters, you may pay 2 life. If you don't, it enters tapped.

Mountain

Lightning Greaves

Equipped creature has haste and shroud. (It can't be the target of spells or abilities.)
Equip {0}

Guttersnipe

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

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.

Birgi, God of Storytelling // Harnfel, Horn of Bounty

Fleeting Distraction

Target creature gets -1/-0 until end of turn.
Draw a card.

Peek

Look at target player's hand.
Draw a card.

Boseiju, Who Shelters All

Boseiju enters tapped.
{T}, Pay 2 life: Add {C}. If that mana is spent on an instant or sorcery spell, that spell can't be countered.

Steam Vents

({T}: Add {U} or {R}.)
As this land enters, you may pay 2 life. If you don't, it enters tapped.

Kodama's Reach

The Great Work

(As this Saga enters and after your draw step, add a lore counter.)
I — This Saga deals 3 damage to target opponent and each creature they control.
II — Create three Treasure tokens.
III — Until end of turn, you may cast instant and sorcery spells from any graveyard. If a spell cast this way would be put into a graveyard, exile it instead. Exile this Saga, then return it to the battlefield (front face up).

Urabrask

First strike
Whenever you cast an instant or sorcery spell, Urabrask deals 1 damage to target opponent. Add {R}.
{R}: Exile Urabrask, then return it to the battlefield transformed under its owner's control. Activate only as a sorcery and only if you've cast three or more instant and/or sorcery spells this turn.

Urabrask // The Great Work

Nyxbloom Ancient

Trample
If you tap a permanent for mana, it produces three times as much of that mana instead.

Tasha's Hideous Laughter

Each opponent exiles cards from the top of their library until that player has exiled cards with total mana value 20 or greater.

Rogue's Passage

{T}: Add {C}.
{4}, {T}: Target creature can't be blocked this turn.

Forest

Vivi Ornitier

{0}: Add X mana in any combination of {U} and/or {R}, where X is Vivi Ornitier's power. Activate only during your turn and only once each turn.
Whenever you cast a noncreature spell, put a +1/+1 counter on Vivi Ornitier and it deals 1 damage to each opponent.

Pyretic Ritual

Isochron Scepter

Imprint — When this artifact enters, 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.

Hedge Maze

({T}: Add {G} or {U}.)
This land enters tapped.
When this land enters, surveil 1. (Look at the top card of your library. You may put it into your graveyard.)

Noxious Revival

({G/P} can be paid with either {G} or 2 life.)
Put target card from a graveyard on top of its owner's library.

Whispersilk Cloak

Equipped creature can't be blocked and has shroud. (It can't be the target of spells or abilities.)
Equip {2}

Tropical Island

Talisman of Impulse

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

Talisman of Creativity

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

Chromatic Lantern

Lands you control have "{T}: Add one mana of any color."
{T}: Add one mana of any color.

Needle Drop

Needle Drop deals 1 damage to any target that was dealt damage this turn.
Draw a card.

Tune the Narrative

Draw a card. You get {E}{E} (two energy counters).

Galazeth Prismari

Flying
When Galazeth Prismari enters, 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."

Exalted Flamer of Tzeentch

Sorcerous Inspiration — At the beginning of your upkeep, return an instant or sorcery card at random from your graveyard to your hand.
Fire of Tzeentch — Whenever you cast an instant or sorcery spell, this creature deals 1 damage to each opponent.

Weather the Storm

You gain 3 life.
Storm (When you cast this spell, copy it for each spell cast before it this turn.)

Brotherhood Regalia

Equipped creature has ward {2}, is an Assassin in addition to its other types, and can't be blocked.
Equip legendary creature {1}
Equip {3} ({3}: Attach to target creature you control. Equip only as a sorcery.)

Bria, Riptide Rogue

Prowess (Whenever you cast a noncreature spell, this creature gets +1/+1 until end of turn.)
Other creatures you control have prowess. (If a creature has multiple instances of prowess, each triggers separately.)
Whenever you cast a noncreature spell, target creature you control can't be blocked this turn.

Farseek

Search your library for a Plains, Island, Swamp, or Mountain card, put it onto the battlefield tapped, then shuffle.

Sol Ring

Fellwar Stone

{T}: Add one mana of any color that a land an opponent controls could produce.

Crimson Wisps

Target creature becomes red and gains haste until end of turn. (It can attack and {T} this turn.)
Draw a card.

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

Open the Way

X can't be greater than the number of players in the game.
Reveal cards from the top of your library until you reveal X land cards. Put those land cards onto the battlefield tapped and the rest on the bottom of your library in a random order.

Charge Through

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

Seething Song

Archmage Emeritus

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

Regrowth

Thought Vessel

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

Stormcatch Mentor

Haste
Prowess (Whenever you cast a noncreature spell, this creature gets +1/+1 until end of turn.)
Instant and sorcery spells you cast cost {1} less to cast.

Ketria Triome

({T}: Add {G}, {U}, or {R}.)
This land enters tapped.
Cycling {3} ({3}, Discard this card: Draw a card.)

Rites of Flourishing

At the beginning of each player's draw step, that player draws an additional card.
Each player may play an additional land on each of their turns.

Mistrise Village

This land enters tapped unless you control a Mountain or a Forest.
{T}: Add {U}.
{U}, {T}: The next spell you cast this turn can't be countered.

Enter the Enigma

Target creature can't be blocked this turn.
Draw a card.

Zhur-Taa Ancient

Island

Exotic Orchard

Dictate of Karametra

Flash
Whenever a player taps a land for mana, that player adds one mana of any type that land produced.

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.

Glamdring

Equipped creature has first strike and gets +1/+0 for each instant and sorcery card in your graveyard.
Whenever equipped creature deals combat damage to a player, you may cast an instant or sorcery spell from your hand with mana value less than or equal to that damage without paying its mana cost.
Equip {3}

Reliquary Tower

Volcanic Island

Stomping Ground

({T}: Add {R} or {G}.)
As this land enters, you may pay 2 life. If you don't, it enters tapped.