You've listed a huge array of skills of which it would take you a long time to truly master. There's little need to start that broad... focus in and specialize. You'll do far better and have a much easier time marketing yourself.
Second from the style of your posts I'd suggest that first place you should start is on your own communication abilities. As a freelancer you are both the executor and the salesman which means being able to build the trust & confidence necessary to land and keep clients through messaging, tone and as you put it "professionalism".
Next is of course your actual skills. There's no shortcut here -- you have to learn and to a degree master whatever it is you will freelance in. What should be a function of interest and innate ability rather than what may be the most profitable; for example if you're strong at creative you'd lean towards design.
Take on free projects, low paid projects, whatever can get you hands on experience and a real portfolio / client list. When you get there come back to us and we'll help with the next phase.