The most important thing is once you have past the cbt theory ,lessons, test etc etc is learn to ride before thinking your Rossie.
I know i said about a 600 straight off but its not impossible depending on your confidence level. i know many people who have bikes but are not a confident rider and will not dream of getting a sports bike or anything else that will do anything except pootling around, on the other hand I got an R6 as my first bike like said and learned to ride on that, the bike will only go as fast as you twist the throttle.(sports bikes are my passion)
I then bought a brand new cbr 600 rr and all my mates where saying get the thou get the thou but I was still happy to learn to ride well on my 600 first.
Did 5 track days and then decided the 600 was not quick enough so bought a 2006 gsxr1000, now that is more than any mear mortle will ever need, but saying that i also own an unrestricted kawasaki zx12R which is mind blowingly quick but like said will only go as fast as i twist the throttle, and it gets used for me and the mrs for weekends away.
I also own a KTM duke 2, now this is my fun bike, its not fast its not slow but boy is it fun, light, managable and so easy to ride, donot discount these when looking at bikes if trails bikes float your boat. wheelies for toffee but also very calm when needed to be.
Do not get me wrong,I only mentioned the 600's because it would just save you getting the 125 then after 6 months, and more confidence thinking I need to sell this, as it sdoes not do what i wanted anymore, and having the hassle of then having to sell trade in again to het the bigger bike. but its all down to YOUR confidence
You start with what ever you feel comfortable on, as in biking confidence is the key, no point getting a bike you donot feel comfortable riding and scared of, another good tip, get the best saftey gear you can afford, i.e lid gloves boots jacket etc etc, you never know one day it might just save your life, theer are alot of idiots out there riding with none to little gear and alot more idiots in cars.
spike