Posting hands, using equilabe, etc, is all excellent advice. I'd also recommend a short subscription to GrinderSchool. The videos made by Carroters can be downloaded and will give you enough to beat up 25nl as a minimum.

As you begin to progress, you can then look into purchasing Matt Janda's book. It's all about how to understand what a balanced range looks like, which then helps you to understand how you can exploit all of the unbalanced players online. I wouldn't buy this book too early in the process though.