The Ooze | Basking Broodscale | Grumgully, the Generous

Cards

Cast
Basking Broodscale by paying ({1} magic symbol) ({G} magic symbol) .
When
Basking Broodscale enters with a +1/+1 counter on it due to
Grumgully, it triggers, creating a 0/1 Eldrazi Spawn creature token that'll also enter with a +1/+1 counter on it.
Activate the Eldrazi Spawn by sacrificing it, adding ({C} magic symbol) .
When the Eldrazi Spawn dies,
The Ooze triggers, creating a Mutagen token.
Activate the Mutagen by paying ({1} magic symbol) , tapping and sacrificing it, putting a +1/+1 counter on
Basking Broodscale.
Basking Broodscale triggers, creating a 0/1 Eldrazi Spawn creature token that'll enter with a +1/+1 counter on it.
Repeat from step 3.

This combo has been estimated to be Oddball (Bracket 2-3+).