Tricky. I think that quite often things like this need to have a declared purpose, so that everyone knows what they are for. Having a secondary aim can muddy waters.
IMO you (and the rest of the members) need to decide if the primary purpose is to save on waste or alleviate poverty, although obviously it will do both in many ways.
How about a 'pay what you can' scheme? So long as it is anonymous, so the usual suspects don't come in and flash a £20 note and those who are most in need are embarrassed ash the £2 they can afford?
A lot also depends on the sort of community it is - if it is a small country village with a mix of residents you can probably do more on trust, whereas in a larger one, or if you will get 'incomers' from nearby towns, you might have to put a limit on the number of items that can be taken at a time/per week.