Cryptic Trilobite has at least two +1/+1 counters on it.
Gilder Bairn does not have summoning sickness.
Mana Needed
({2} magic symbol) available.
Steps
Activate
Gilder Bairn by tapping it, adding ({GU} magic symbol) .
Activate
Gilder Bairn by paying ({2} magic symbol) ({GU} magic symbol) and untapping it, doubling each counter on
Cryptic Trilobite.
Activate
Cryptic Trilobite's first ability by removing a +1/+1 counter from it, adding ({C} magic symbol) ({C} magic symbol) that can only be spent to activate abilities.
Repeat.
Once you have infinite +1/+1 counters on
Cryptic Trilobite, you may instead double the counters on any other permanent(s).
Results
Infinite +1/+1 counters on
Cryptic Trilobite.
Infinite colorless mana that can only be spent to activate abilities.