Jothar:
It is a curse to give to those who do not need, and you do not get Schar, straight out gemorah Bava Basra 9b. You are better off paying taxes (for which you do get Schar, see same gemorah prior amud).
Personally, as I have said on other threads, my strict priority is to give to those within my community & to local yeshivos, but give something (very) small to all those who come around (which doesn’t happen often), whether they are “kosher” or I’m not sure. If they have a letter from the Vaad I will give somewhat more, but explain (when they want more then that) that the local community is my priority.