I think to maximize the goo, if you're not that hard up for cash, is to leave as many characters on tasks walking around your town. It's amazing how quickly they will be possessed (which I think is a really neat little graphic on each character). Then you can tap them for Goo. So if you leave some ghosts out there, given a chance, and depending on how dense your town and roads are, your characters can pick you up a lot of extra Goo. Pretty neat to come back after several hours (gasp!) and see all the ghosts and possessed town folk.
