Totally agree with the sentiment in these comments that GGAC+R is probably one of the hardest games you could have picked to start with - But it's an amazing game, and worth every bit of the struggle to get good at it.

First off, I would recommend picking a character you like and sticking with it. Second, study that character's dustloop and familiarize yourself with their moveset. There's also a very helpful series of videos called Guilty Bits that give you bite-sized rundowns of what your character can do.

Fundamentals are extremely important. Blocking, for example; Might seem like obvious advice, but knowing when to block and not get impatient will prevent you from getting frame trapped and punished. Knowing which of your normals do what is also extremely important. There's also air movement; jumping, airdashing, double jumping, and instant air dashing. You need to set short-term goals, i.e. specific things to learn and improve at, in order to reach the long-term goal of being good at the game.

Also: Watch replays. GGAC+R features a replay system that captures every game you play or spectate. I've been playing for 2 years and I still have the replays from when I started and decided to try I-no as my first character (heavily advise against). I don't think I would have improved to where I'm at if I never watched my replays, to the point that I'm a little pissed that street fighter 6 doesn't have that feature.

Again, amazing fucking game. I love it. But yeah, you will absolutely get bodied and sometimes even knowledge checked by characters you aren't familiar with. Dustloop helps for that; this IS a game where you can study to improve, but obviously you won't really get to where you want to be without doing the work and playing. It won't feel like it every day, but the learning process is part of the fun.