Once you mastered the basics (opening/closing files, navigating, basic editing) just use it. As with a lot of other tools, practise makes perfect...
I would, however, set some time aside to work on improving how you use the editor currently, but as part of your normal workflow as opposed to just going off on a tangent and learning things for the sake of it.
I find some useful resources are the EmacsWiki and the Planet Emacsen blog. I use both, mainly by using Planet Emacsen for "inspiration" and then wandering over to EmacsWiki and having a trawl on there for a specific topic. I found that unless you're having at least a vague idea what you're looking for, the available information is just going to swamp you instead of it actually being helpful.
Not to mention that there are a few very useful resources here on StackOverflow, for example this question here. Emacs is a very powerful tool that tends to be able to do a lot more than a single person needs, but in the end that allows you to pick and choose exactly those parts that you need.
