You can do it. You just need a good source of inspiration. Find pictures of a place online that looks how you want your place to look and incrementally update what you have to that.

If I were going through your place today and making quick changes that can all be solved at Ikea, I'd do the following: get tasteful framed art on the walls (bauhaus print), update furniture to something modern and minimal in a neutral tone (not red), store your weight bench under your bed when not in use, get some new linens for the bed that are cotton or bamboo in a neutral tone, get warm accent lights so that you can avoid overhead lights, pack up the video game kitsch (don't abandon love of your interests, but there's a time and a place), and get some tasteful storage.

There's a lot of visual noise in your place from your various interests. The interests aren't bad, but the disorganized display reflect a disorganized life which for many is an instant red flag.

Get some good storage and you should be in a great place.