You may start off as a Knight, but realize you prefer magic and spells, so then you can rearrange your attributes to be a Sorcerer. Another important thing to know is that the class you pick can change entirely as you play the game. The good news is that your looks don’t affect the stats of your character.
There’s no way around this, so you just have to accept the fact that you’ll spend the rest of your playthrough being extremely ugly. The first thing you’ll notice is that every player model is absolutely hideous. Like many games, Dark Souls 3 allows you to create your own character and choose your class.