Gilder Bairn + Gemstone Array + Earthcraft

Gilder Bairn

Gemstone Array

Earthcraft

How it works

1. Activate a basic land by tapping it, adding one mana.
2. Activate Earthcraft by tapping Gilder Bairn, untapping the basic land.
3. Activate the Forest or Island by tapping it, adding one mana.
4. Activate Gilder Bairn by paying 2G/U and untapping it, putting at least three charge counters on Gemstone Array.
5. Activate Gemstone Array twice by removing two charge counters from it, adding 1G/U.
6. Repeat from step 2.
7. Once you have infinite counters on Gemstone Array, you may instead double the counters on any other permanents.