I’m pretty crappy compared to a lot of people here, and I’ve only been playing about a year and a half, and mostly online, but here’s some advicce anyway.
Don’t call Yun a cheeseball character. Ken is considered better than Yun by some of the best players these days, or at least as good. Yun is also really hard to learn how to use well, where other characters have a much easier time cheesing in lag (Urien and Alex especially). I suppose that’s just my opinion, but even doing Yun’s bnb (and finding legit ways to start it) seems way harder to me than any other character’s mandatory damage dealing methods. Also, people drop on Yun a lot, which is pretty frustrating for me especially, because I have way too many subs, and I’m not even good with Yun so usually when I’m winning I feel like I deserve it…
Also, don’t get hung up on parries at this stage of the game. Learning to block well is way more important. Learn how to parry stuff in training mode, sure, but don’t be too stressed about using it. Parrying is almost always a risk. Knowing how to parry stuff is great, but it’s not mandatory very often. If you watch high level play, you’ll see a lot less parrying than you see from a lot of online players. Honestly, I still suck at it a lot, but I’m at least good enough that I win around 60% of my ranked matches; which is sort of a meaningless statistic, but it’s better than the 1/4 I was sitting at for the first few months I played. I don’t understand how some people parry so much online, because in lag I can’t even parry spammed moves consistently.
For you main, basically everyone except Sean and Twelve are viable, but if you actually want to get good at the game please do not use either of them. The odds of there being a breakthrough 16 years into this game’s life for either of them seems quite low. I’d mess around with learning bnbs and basic gameplay strats for whoever you find fun, and when you start feeling like you’re using somebody correctly, stick with that character. That’s what I did with Dudley, anyway. He was the 5th character I tried to main, and things went better with him than Yang, Q, Akuma, or Yun pretty much instantly, so I stuck with him. I still sub way too many characters, but I try to at least use Dudley somewhat every time I play.
Oh, and don’t try to start out with Akuma either, he’s too complicated. Learn Ken or Ryu before learning Akuma, because their basics apply. People told me that, and I got super angry, thinking they were being condescending. But it turns out its true. Akuma has tons of tricks that there’s no sense in learning at the point of the game you’re at. You’ll always be able to cheese some people with jump back fireballs online (I still struggle against it with dudley sometimes), but that kind of play doesn’t foster improvement. Also, pretty much everybody online (including me, when used him) gets way too greedy with Raging Demon and KKZ. They are RARELY worth using. His SA1 is a better option 90%+ of the time. His EX supers are satisfying, but very hard to guarantee. People use them as hail marrys way too much online, and you’ll wind up throwing the match against players who are paying attention. I can’t tell you how many times I’ve been about to lose to an Akuma, but I won instead because I baited KKZ, which gave me free EX machinegun combo.
Hopefully some of that was useful.