Welcome to KI, OP! Also, welcome to the boards. Hope you enjoy both.
As far as which character to use, I’d echo the sentiments above in saying that Jago’s good to start with. Run through the dojo mode first. You don’t have to do all of it, especially the final lesson, which is rather difficult for beginners, but get through all of the basic mechanics for sure.
After that, you can either stick with Jago or maybe branch out to some of these easier characters. Mind you, when I say easy, I just mean easy to pick up, as every character has tons of depth beneath the surface, including Jago.
Jago: Easy to pick up because of his similarities to Ryu in Street Fighter. If you know Ryu, you should know some of the basics for Jago, like his fireball, his kick special and his dragon punch. That should help get you started.
Sabrewulf: His back-forward and up-down special move directional presses make him an easy character to start off with. Same goes for his combo trait, which basically allows you to press the same button over and over again before ending a combo.
Other easier characters include:
Also, don’t be afraid to use combo assist by pressing X on a character at the select screen. This will take the directional press out of a special move so instead of say, having to press d/f A, A, d/f A, A, d/f right trigger to do a combo, you can just press A,A,A,A,forwrad and right trigger.
It’s easier to do in the beginning and it gives you the general cadence to a combo as well as what it’s supposed to look like. You’ll want to turn this off eventually, as it can make doing more complex combos a bit more difficult, but as a way of just introducing yourself to the game, it can be helpful though in truth, some think it helps new players develop bad habits, so judge for yourself.
Hope that helps!