Kawasaki H2 , Suzuki hayabusa , Kawasaki zx14r

Thank me later.

bmw s1000rr or no thank you

250 = learner, not all that fast, super cheap so if you drop it oh well (these are for sale all over craigslist, fb market place, prolly your local news paper dont buy a new 250)
600 = can learn, goes fast, wont outgrow it so fast.

ninja 400

/close

cbr650F if you can find one. good power and better rider positioning to make it a good cruiser/commuter but still sport style with plenty of power.

take the one you like best. you learn with anything, and you learn even more by following friends. I started with a 2006 ninja 636 and ended up with a ktm rc8r, trying ducati 848, ninja 1000, ktm adventure, gsxr 600 and more.. it will be all relative and all a matter of habit, I noticed that the saddle of the ninja 636 is taller than many bikes, but it never bothered me, but there are those who bother, so don't ask others how they are, just have the experience on your own. one thing that may please me it is not said that you like it .. let us know what you get;)