Emerald Medallion

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

Gruul Signet

Mana Crypt

At the beginning of your upkeep, flip a coin. If you lose the flip, Mana Crypt deals 3 damage to you.
{T}: Add {C}{C}.

Mishra's Workshop

{T}: Add {C}{C}{C}. Spend this mana only to cast artifact spells.

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.

Arcane Signet

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

Sol Ring

Thought Vessel

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

Flubs, the Fool

You may play an additional land on each of your turns.
Whenever you play a land or cast a spell, draw a card if you have no cards in hand. Otherwise, discard a card.