Trusty Boomerang + Mana Echoes + Chishiro, the Shattered Blade + Smellerbee, Rebel Fighter

Trusty Boomerang

Mana Echoes

Chishiro, the Shattered Blade

Smellerbee, Rebel Fighter

How it works

1. Cast Trusty Boomerang by paying 1.
2. When Trusty Boomerang enters, Chishiro's triggers, creating a 2/2 Spirit creature token.
3. When the Spirit enters, Mana Echoes triggers, adding C for each Spirit you control.
4. Activate Trusty Boomerang's equip ability by paying 1, attaching it to the Spirit token.
5. Activate the Spirit by paying 1 and tapping it, tapping a creature and returning Trusty Boomerang from the battlefield to your hand.
6. Repeat.