Find a couple characters that you enjoy and stick with them for awhile. Get good with them and you’ll naturally learn the skills that are shared between all fighters. After you’ve got that down it becomes much easier to pick up new characters since the basics are all shared. You should also have a feel for other characters special moves since presumably you’ll have played against them a number of times. You won’t be great with a character you never play, but you don’t have to worry about not knowing any of their combos or anything. I consider that to be one of this series greatest strengths, once you are fully comfortable with the basics, you should be able to have fun with any fighter.
Learn when to use the different kind of attacks, practice dodging/shielding, and stay mobile. I think a lot of that comes naturally with practice.