I've got a friend who is a seriously successful fanfic author, and we have had this exact conversation. And it is circular. You cannot (by definition) make money writing fanfic. So it is ultimately pointless. Becoming a better writer is only done by writing. Writing fanfic is writing. Return to 1: repeat. There is no "right" answer, of course. But it is an important question to ask yourself from time to time. "Am I spending my time on the right things?" The right things are, reading, writing, and creating. Sometimes you will be doing 80% of one thing (writing) and only 20% of another (reading). You can't sustain that, so you need to make sure to measure yourself, ask "Am I doing the right thing right now?", and then do The Right Thing, whatever it is. I've got Discworld fanfic I have written. It really is a great story about Nobby Nobbs accidentally becoming a legitimate businessman. But... what do I do with it? Good questions to ask yourself. Just don't stop asking these kinds of questions, and you will be healthy.