I've had luck with anywhere from a dozen to a hundred. If Im hunting along a river or even in a sandpit or something like that, I tend to use somewhere between 15-25 goose decoys and I usually throw out some duck decoys as well. Hunting with my buddies in cornfields, we have put up well over 100. Investment wise, I use Green Head Gear decoys myself. Depends on what your willing to spend I guess.