If you did all the basic learning paths, I would suggest to work on the Microflow and Domain Model paths. Data Structure and logic is very important in every app.
If you are used to it, you can pick up whtaever sounds interesting to you. But my personal suggestion is: Play around and try things. You may break stuff but this is an essential part of learning. If something does not work as expected, ask a forum question. (And don’t forget to commit often)
Do you have any developing experience? Working with algorithms, databases, ER models, SVN? If not you should propably start step by step with the tutorials to not miss anything. If you already have experience, then you should take a look for the description of the toics and select what you are not familiar with or you are interested in.