Activate Necrotic Ooze using Garth One-Eye's ability by tapping it, causing you to pay ({0} magic symbol) to cast a copy of Black Lotus.
Activate Black Lotus by tapping and sacrificing it, adding ({G} magic symbol) ({G} magic symbol) ({G} magic symbol) .
Activate Necrotic Ooze using Barrenton Medic's second ability by putting a -1/-1 counter on it, untapping it.
Activate Necrotic Ooze using Garth One-Eye's ability by tapping it, causing you to pay ({1} magic symbol) ({G} magic symbol) to cast a copy of Regrowth.
Resolve Regrowth, returning Garth One-Eye to your hand from your graveyard.
Activate Necrotic Ooze using Tireless Tribe's ability by discarding Garth One-Eye, giving Necrotic Ooze +0/+4 until end of turn.
Activate Necrotic Ooze using Barrenton Medic's second ability by putting a -1/-1 counter on it, untapping it.
Repeat.
Once you have infinite ({G} magic symbol) , you may sacrifice Black Lotus for any other color of mana, and use that to cast any other spells from Garth One-Eye's ability.
Results
Infinite Black Lotus tokens.
Infinite card draw for any number of players.
Infinite casts of all spells permitted by Garth One-Eye.
Infinite colored mana.
Infinite creature tokens.
Infinite draw triggers for any number of players.
Infinite magecraft triggers.
Infinite self-discard triggers.
Infinite storm count.
Infinite ETB.
Return all cards from your graveyard to your hand.
Infinitely powerful Shivan Dragons until end of turn.