There are as many different answers to this as there are different people or jobs. But to put it super simply learn how to do something that people need done, and not everyone can do.

I personally believe a formal education (either through traditional university or a more trade based education pathway) is the best choice for a large majority of people.

Figure out a realistic plan to increase your earning potential. I remember working my ass off when I was around your age for near minimum wage. 10 years later, I make in an hour what I used to make in an 8 hour shift. All that overtime seems kinda silly now.