Nursing school is very tough which we all know. As far as it goes on what to study up on for your first semester, I really couldn't gear you on what to focus on cause every nursing curriculum is different but from my experience, my first semester was mainly based on the whole model of nursing and basic nursing skills which you really can't study up on. My first semester of school was the beginning of learning the nursing process which is (Assessment, Diagnosis, Planning, Interventions, and Evaluation). The nursing process is a method that nurses use everyday which a huge part of nursing school will pertain to this and critical thinking. I really don't know how you can study for that but you could possibly familiarize yourself on a little of what nursing is all about.
While you are waiting to enter nursing school, as of now I will just relax and enjoy yourself. Nursing school can be very stressful but you seem very willing to take on the task. When you start nursing school, try to develop some very good study habits and test taking strategies cause they can be very important and useful. You are doing the right thing by trying to prepare yourself and just don't ever let yourself get down during school. If you really want to be a nurse then you will be a nurse.