Sagat isn't OP. He's slow but does good damage if you don't mess up the Tiger wall and can reliably do Tiger Uppercut FADC Forward+HK Ultra. Sagat takes a fair amount of work to be any good with due to his limitations. I'd pick Ryu if I was you. Good reversal move, good damage on meterless combos, and a few reliable ways to land his ultra (AA LP Shoryuken Ultra1, LP.Shoryuken FADC Ultra1, Facing the corner EX Tastu Ultra1, etc).
Or, you can pick someone like Rose (my main) or Dhalsim that will teach you how to do a few things well without relying too much on long ass combos.