({G} magic symbol) ({G} magic symbol) plus an additional ({G} magic symbol) if you don't control an untapped green creature available.
Steps
Cast a copy of
Channel by paying ({G} magic symbol) ({G} magic symbol) .
Activate the ability granted by
Channel four times by paying 4 life, adding ({C} magic symbol) ({C} magic symbol) ({C} magic symbol) ({C} magic symbol) .
Cast
Sprout Swarm with buyback by paying ({4} magic symbol) and either tapping a green creature if you're able or paying an additional ({G} magic symbol) .
Aetherflux Reservoir triggers, causing you to gain 1 life for each spell you've cast this turn.
Resolve
Sprout Swarm, creating a 1/1 Saproling creature token and returning
Sprout Swarm to your hand.
Repeat from step 2.
Notes
The life requirement can be lowered if you've cast spells beforehand this turn and/or if you supply additional mana. After the first loop, you'll want to tap the Saproling to reduce
Sprout Swarm's cost by ({G} magic symbol) via its convoke ability.
Results
Infinite ETB.
Infinite colorless mana.
Infinite damage.
Infinite lifegain.
Infinite magecraft triggers.
Infinite storm count.
Infinite tapped creature tokens.
Bracket Tag
This combo has been estimated to be Exhibition (Bracket 1+).