Get a medium/light weight medium/bland performance bike to start with. Big cruisers are not forgiving and you're not going to muscle your way out of errors (and it's always good to have something you can stand up by yourself without having to ask for help). High performance squids are not forgiving either -- crank the throttle or jerk the wheel inadvertently and you don't even have time to go "o sh...". Get a used one that won't make you cry when you roll onto your friends deep gravel driveway and it falls over. Wait until you feel comfortable with it and scare yourself a couple of times. By then you will have a much better idea of what you want/like. Sell it and buy a new one that's right for you.