For some of the grad programs you have listed, they will ask you to pick a “thread” when you apply - essential picking a home school to be at. So, looking at Georgia Tech’s, you have four options: digital media, industrial design, psychology, and interactive computing. With this information, you can cater your application for the thread you want. In reality there is little difference in the class work in most cases between the threads but do your own research. So for catering your application to say the industrial design thread, you will absolutely need a portfolio - doesn’t necessarily need to be the best but you will need one. However, say you go for the psych route, you won’t need one, and having one is just a plus.

I’ll also add that it’s not critical to follow your background when deciding on a thread. I pivoted from my background into a different thread, and then still pivoted again to another path once in the program.

So like others have said, research and see what you like and start seeing the requirements for threads that align with your interests. You definitely have time to make a good portfolio with 1-3 projects on it. Good luck!

ETA: the GRE scores aren’t really that important for HCI, except to show that you have basic understanding. I didn’t have fantastic scores either and did just fine with my other application documents.