Elena, CONTRIBUTE is used most often when there is already a fund, for instance, and you add to it. It doesn't sound idiomatic in reference to the needy, because it's assumed that they don't have a running fund :) The more idiomatic verb is GIVE in this case, because you literally provide money to those who don't have it.

Things you contribute to: a political campaign, a collection for someone who had a medical emergency, an education fund for a child, a cause that maintains a fund to help a certain class in need, e.g. battered women, orphans after a catastrophe, refugees of a war, etc.