It can be tough just starting out, I know, because I am lol. When I first started I couldn't really beat anyone on FG either, my crappy internet didn't really help, but that's another issue. I can only give you broad strokes advice really, which is probably all you need.
I'd personally try to become better at the basics of the game. Like spacing out your attacks, becoming more accurate with your attacks, becoming less predictable, punishing your opponent's unsafe options. I personally don't think character choice makes that much of a difference in your situation, play who you like to play and that should be fine.
Watch videos of matches and tutorials, read things about the game, etc.
Practicing the game will help of course, find friends to play with and if that's not an option IRL find some folks online who won't mind helping you train up some.
And finally, don't let the losses get to you mentally, learn from them then let it go, don't get too upset about losing because if you commit yourself you will get better, no doubt.
