It depends on your classes and teachers. I'd say start out with a binder for each class with half of a pack of loose leaf paper in each binder. You really don't need any notebook unless you prefer them to binders, in which case you should get a notebook for each class instead of a binder. I, personally, like binders better because they can also store handouts from teachers. You will also need about five pens, three pencils, a graphing calculator, and anything else specifically assigned by the teacher.
i just used 2 five subject notebooks and used one subject of the notebook for each class. make sure you have a pencil or pen. other than that if you need other things your teachers will tell you what you need for their class.