The first thing
you should do is produce portfolio of online work or apps that you can show people - potential clients.
If you haven't ever worked in the field ,get a job and find out what is required to do the job professionally. You will get exposed to things you never thought about and become better .
Think about what you would want to see from someone you were hiring to do a job or a project. You want somebody with a track record
In terms of games , Java is not the way to go . Look at Unity or something similar .