I've made my character with a long term planning in mind. I somehow already envisioned her to be the mischievous little devil that on the surface is oh so sweet (and Miley's smile seemed to match exactly how I had in mind), though she originally was going to have blue eyes along with the black hair, but somehow green suited her better, especially after being sorted in Slytherin.

So far she seems Mary-Sueish but in seven terms, a lot can go wrong for her during those terms. So right now, I see Kimalia as being quirky and cool, but a perfectionist and since she's use to having it easy in life it'll make it more difficult for her to deal with when certain events happen with her.. So for now, everything's peachy with her.

I think it's fine if you wish to start out with the perfect character, as long as you plan out how what you're going to have them as during their school years. I can imagine it being pretty boring when you continually play as the same character without much change to their personality, so don't be shy in changing things up and make them complex!