Not sure if this will help on that small of a budget, but one thing to bear in mind is that having some different seasonings (sriracha, curry powder, etc.) can make the same stuff "stretch" -- in the psychological sense -- a lot further.

EDIT: I realize the OP is about actual food, but I guess the angle here is you could buy a larger quantity of a cheaper -- but boring -- food and still keep your sanity. :)