If you want to work in the gaming industry as an artist, you should first answer two questions:
1.What exactly do you want to create? Characters, weapons, transportation, environment?
These spheres sometimes overlap, but you should still choose something particular for a jump start, as it determines the knowledge and pipelines you’ll need to master.
2. In what style do you want to work?
Indeed, the style has much in common with realism; these are not two distinct areas, and at some point, you can transfer from one to another. But when it comes to your portfolio, you should determine what you’ll show to a prospective employer.
Do you want to work on Overwatch-style products? Then look for references and concepts of artists who worked on them. Shape your portfolio in this style.