Farmstead Gleaner and Omen Hawker in your graveyard.
Necrotic Ooze does not have summoning sickness.
Steps
Activate Necrotic Ooze using Omen Hawker's ability by tapping it, adding ({C} magic symbol) ({U} magic symbol) that can only be spent to activate abilities.
Activate Necrotic Ooze using Farmstead Gleaner's ability by paying ({2} magic symbol) and untapping it, putting a +1/+1 counter on it.