How should I be fair in regards to beggers?

I am putting this in General because I don’t want it to turn into a debate over whether people should “get a job,” etc. Thank you in advance.

Paris is the only big city I’ve ever lived in, so I do not have much experience with being confronted with many beggers on a daily basis. There are a good deal of homeless people in my hometown back in the States, and I will often give them leftovers if I’ve been eating out, or cigarettes, but I avoid giving money.

Moving around in Paris, though, I see beggers everywhere: on my own street, on the metro, etc. Sometimes entire homeless families—probably Roma. I feel especially bad to see obviously Muslim beggars during Ramadan. I know that there are many other ways to help, and maybe I will volunteer in a food pantry or something like that while I am here. I think of giving money to beggars as a religious duty, but I also am living on a student budget and can’t go completely nuts.

Can you help me come up with a rule for giving to beggers while I’m living here, that won’t leave me completely bankrupt? Is it a fair rule to limit myself to giving to one begger per day?