there is no one particular path way or a one size fits all solution, it depends on your choice and your requirements, instead of asking what to learn next, you should ask yourself should you really learn a particular thing today, or is this a scene from a different chapter of the book and should be done later.

i just have one simple saying about the subject selection which i wish to learn "when you have removed a subject which is not a immediate requirement , what ever remain not matter how difficult it is, must be learned".