I used textbooks, course notes, and occasional review books. Occasionally I'd supplement with journal articles.
The completeness of your course notes really depends on the school. You need a very solid foundation for step-1 because so many questions are multi-step, integrated type, and require more than simple recall. Remember that 2nd year is way more important for the boards (at least it was for me).
I studied for about 5 weeks with the Kaplan books, managed a 257/99.
p.s. My opinion is that using the Kaplan books during ms1/ms2 will help so long as they are a supplement. Texts are usually better as a primary source.
p.p.s. You probably don't need a textbook for things like biochem, cell bio, molecular, etc., esp. if you covered that in college. But they are essential for path, physio, pathophys.
best of luck