Difficult question(s). First of all, practise and practise. Do many small projects. Show your work to get feedback. Learn 3D concepts. Learn tools. Learn programming languages.
Just start with a simple game, like tetris. Learn project management. Learn how to publish games, etc.
So the real questions is, what do you like to do? Yeah, building a game … do you have an idea. Did you write some user stories for development … so much to do and learn. Start small, step for step.
Have fun
See: Taking your skills to the next level - or, Planning for a future in 3D