Best bike for beginner?

I really want a motorcycle and and planning on buying one. I have a motorcycle enthusiast stepmom who will teach me on dirt bike and work my way to a street bike and I will be buying one when I'm ready. I'm thinking of a ninja 650 or 400. What's my best option. I don't want a slow bike or something too crazy and it has to be sporty looking. NO CHOPPERS OR HARLEYS. I am 5,6 rn and 180 pounds. I'm planning on losing weight