Flame Jab + Polyraptor + Mana Echoes + Groundskeeper + Chromatic Orrery

Flame Jab

Polyraptor

Mana Echoes

Groundskeeper

Chromatic Orrery

How it works

1. If Flame Jab is in your graveyard, cast it for its retrace cost by paying 1 and discarding a basic land card, targeting Polyraptor.
2. Otherwise, cast it by paying 1, targeting Polyraptor.
3. Resolve Flame Jab, dealing 1 damage to Polyraptor.
4. Polyraptor triggers, creating a token copy of itself.
5. The Polyraptor token enters the battlefield, triggering Mana Echoes, adding C for each Dinosaur you control.
6. If you cast Flame Jab from your graveyard, activate Groundskeeper by paying 2, returning a basic land card from your graveyard to your hand.
7. Repeat.
8. Once you have infinite mana, you may instead target any other target using Flame Jab.