These are the ones that I use. It comes to about to about .13 cents per package and they fit up to 6 mini figures. They probably won't work for sets, but polybags would definitely fit in there!

(http://www.amazon.com/gp/product/B0040ZFXLC/ref=oh_details_o01_s00_i00?ie=UTF8&psc=1)