I am 14 and want to be a pilot but don’t know how
PPL is a very good choice to begin with your pilot career. 
- You got quite a good knowledge which will be really usefull when you go for the CPL. 
- You begin to collect flying hours (which is the most important thing to get a job).
- And you may realize if you are fit to fly (sometimes wishes don't match reality).


University is fine, but afaik nowadays airline companies don't ask for such degree when you apply for a job. However, it'd be a bonus.
Competition was hell years ago ('07-17), in particular for those with very low flying hours, never the less, currently companies are hiring a lot.
Sorry but I know nothing about VCE (I'm not aussie), but, if I can change your question to ' What should I begin to study to get ready for PPL/CPL?', then I'd say that you must get ready for the two subjects which trouble the most students. Principles of flight, and General Navigation. 
I don't know if they are out of reach from your current knowledge, but, you may give it a try. I'd suggest you to use the Oxford books, or Jeppesen ones. Both are really good ones.
And about the stages, in my opinion:


PPL (fly as much you can)
CPL 
Try to get a job (probably Flight Instructor (get FI license)
Apply for a company



Good luck