So assuming you've been reading diligently (starting from lesson 0) and have followed the instructions of completing only the recommended number of pages, then you're probably wondering, "what do I do now?"
Well, the smart thing would be to get your homework reviewed. Let's say you've done that already, and want to know what your next step is going to be.
I would recommend tackling the 250 box challenge next. This exercise will take what you were introduced to in the rotated boxes and organic perspective boxes exercises and work on developing your overall grasp of, and comfort with, freely rotating forms in 3D space. The notes and video there cover techniques that will help you do this as efficiently and effectively as possible as well.
It's a tall order, but most who've gone through it have shown considerable improvement - especially those who've read through the notes and applied the error-checking approaches consistently.