No matter what app, tool or package you use, the most important thing is the actual basic fundamentals of any and every topic. Only after that, you use tools to implement and showcase your art skills.
"In my opinion, for a game artist, your portfolio should be all about showing how well you know your craft, not how well you can use a tool - that is for technical artists.
"Learning tools will make you proficient with getting your work done, but being artistic, for example having a sense of 3D space – for environment artists – or knowing the anatomy – for character artists – are the parts that make you a good artist.
"With that said, you should choose whatever tool that you are comfortable with, and learn it as you go. Do not be afraid to switch tools to try out different ones. If you ask me for recommendations, I would suggest using Unreal Engine 5 as your engine to build, render and showcase your artwork because if you start learning it, you will be exposed to learn a lot of concepts and features that will be very useful for your career as an artist.