Even if you work smart you still have to work hard. Skills aren't the types of things you can check off as mastered and then move on, you need to keep working on improving them continually.
My suggestion would be to create different projects for yourself that combine the concepts you want to focus on. For example, create a short animation of someone tripping and falling over something. You'll practice anatomy by putting effort into creating the character model, physics to make the fall look believable, and the 12 principles of animation to make the short appealing. And you'll end up with a possible portfolio candidate to boot.
Also, check out Animation Mentor. You need to pay for the actual program, but they have a lot of helpful resources for free.