Then you need to try to get access to your school's weight room. You can do the cardio part without any equipment, but the weight training you will need the equipment. As a student there you have a right to use the equipment, you don't have to be on a sports team.
Without the equipment you are not going to be able to do much more than cardio, Check out the classifieds in your paper, there are always people looking to sale weight sets that they bought and don't use anymore. You can usually find those for almost nothing. Ask around also, maybe someone has a set that is sitting in a garage or basement that they will just give away, to get rid of them.
Nothing, about the only thing is db curls, but there is no way that you can do enough to be any benefit to you. On your own without equipment I would say run sprints, do push-ups, pull-ups, and ab work, but none of that will gain you any mass. It will just help condition you.
I can give you a smart ass answer or the truth, and I am not in the mood for being a smart ass.