This guide is all about maximizing your income, which is how you get lots of tiles. Follow it and I think you will fill up 2 islands. One extra tip: large red tiles are the most efficient to upgrade. I try not to waste actions on upgrading green, yellow, or small tiles. The borderline tiles are red 4 space, yellow 9 space, and green 9-12 space. By upgrading I mean the up arrows, not crafting actions.