Get an old t-shirt (white perferably). Rip that **** up. Get some ketchup, spread it all over. Get some dirt (i bumume you can find some dirt) spread it all over your face. Mess your hair up. Wear ripped jeans if you have them. Oldest shoes you have. Get something that looks gun like (or get a toy one from a dollar store if you want.) And your a proud survivor of the zombie apocalypse.

Cost: $0 (or one if you want to get a dollar store gun)

Effort: 0 (most of your clothes are already ripped and ketchup stained already, most likely.)