Any reccomendations on how I should manage?

I just finished my AP chemistry class and got a 5 on the AP test. Being the helpful student that I am, I am seeking to make an AP chemistry help site. I will be going through my whole book and will be trying to give methods of memorization etc. that have helped me get through the course.

The problem is that I'm not a great web designer, sure I know a bit of html and how to do a layout with tables, but nothing you can't learn in a highschool "web design" course.

I was in notepad putting out a very simple design when I realized it wasn't nearly enough to accommodate what I was planning to do.

Does anyone have recommendations as to ideal content management programs I could use to say add pages easily with long content and multiple linked pages per update? I would also like a categorization system.

Of course, being a student, I have a very tight budget, I would like it if the script was free (I know this is like looking for gold in a coal mine, but I can dream can't I?).

Any help is appreciated, thanks!