If you're playing Pathfinder and looking for some rule support, there is the
Pathfinder SRD. As a GM and as a player, I use this ALL THE TIME. It is super convenient. And if you need info on Golorian (the world that Pathfinder defaults to), there is a solid
wiki for that. Also used heavily. These will help you to at least keep the costs down while you learn.
As said above, it's hard to teach the game without being there. Best way I've found to learn the game is to play it and to read the rules. A solid grasp on the rules is never a bad thing. However, if you have some specific questions, ask away. Just be as specific as you can on what edition you're playing.
Editions from latest to oldest run like this DnD Next (are they calling it 5th Edition yet?), Pathfinder, 4th Edition, D&D 3.5, D&D 3.0, AD&D 2nd, AD&D 1st, D&D, Red Box D&D. (Did I miss any? I feel like I missed one in there...) You might not know which version your'e playing, but I bet if you can describe a few books, we can collectively narrow it down.