A high economy strategy: Invest 2 lines of money generators. Keep them lvl 1 and upgrade to lvl 2 only once you have set up basic defense. For the defense put 3 lines of walls and two lines of turrets. With the high earn rate you can spam the repair button (early on just let the walls die and rebuild them). Upgrade defense when you have extra money. Once you get to 500+ mind energy you can start spamming attack with mixed colors on 3 lanes.