Rhystic Study

Whenever an opponent casts a spell, you may draw a card unless that player pays {1}.

Lotus Cobra

Landfall — Whenever a land you control enters, add one mana of any color.

Command Tower

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

Chulane, Teller of Tales

Vigilance
Whenever you cast a creature spell, draw a card, then you may put a land card from your hand onto the battlefield.
{3}, {T}: Return target creature you control to its owner's hand.

Sol Ring

Arcane Signet

Cyclonic Rift

Return target nonland permanent you don't control to its owner's hand.
Overload {6}{U} (You may cast this spell for its overload cost. If you do, change "target" in its text to "each.")