If you really like these people, if you enjoy being around them, hang out with them, just don't keep giving them stuff. Once you say no a few times you'll see who's real and who's not.
I had a lot of friends like that in college, they were always wanting food, money, drugs, etc. and it was annoying but it's what people do at that age because they don't have much money. And sometimes other people did things for me too but you have to put yourself out there for it. College especially is like that, it's like there's a complex bartering system.
People like that won't ever seek you out, unless they want something. It's nothing to do with you, they just have a mindset that everything should come to them and they don't ever think about giving to other people. Some will reciprocate if you ask them or remind them that they owe you a favor. I have never been good at negotiating things like that that which is why I get tired of it. But seriously at that age you are going to run into that a lot.