What amount of cc's is good for a beginning rider?

Everyone always says to get the Ninja 250 or the Honda CBR250R. Others say you'll get bored with the 250, get a 500cc or a little smaller. For me, that bike would be the Honda CBR500R. Everyone says it depends on your weight. Right now, I'm on average about 105 pounds. But I wanna gain up to 125 pounds. BMI said so… I'll gain that weight before I get a bike because I wanna wait a couple years before I buy one anyway. I live with my mom and she would never let me buy one. But I'm learning to live on my own. So, the real question is… What is a good starter bike for a 125 pound man who has never driven a motorcycle or dirt bike? I really don't wanna start on a 250cc or 300cc. 400cc's to 500cc's is where I wanna start. But give me your opinion.

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