You control a creature with a +1/+1 counter on it.
({2} magic symbol) available.
Steps
Activate Ghave's first ability by paying ({1} magic symbol) and removing a +1/+1 counter from a creature you control, creating a 1/1 Saproling creature token.
Sigil Captain triggers, putting two +1/+1 counters on that Saproling.
Activate Ghave's first ability by paying ({1} magic symbol) and removing a +1/+1 counter from a creature you control, creating a 1/1 Saproling creature token.
Sigil Captain triggers, putting two +1/+1 counters on that Saproling.
Activate Ashnod's Altar by sacrificing a Saproling token, adding ({C} magic symbol) ({C} magic symbol) .
Repeat from step 3.
Once you have infinite colorless mana, you may activate Ghave infinite times.