Doesn't matter what size bike you start on (250,600,750,1000 or more) so long as you can respect the bike, what it can do, and the fact that what the bike can do, isnt always what YOU can do on the bike. Ride within your limits.

I started out on my rc-51 and it's as big a torque monster as 1000cc sport bikes get... and I love it. Best advice I can give, is to budget at LEAST $650 or so for a quality helmet and riding gear. Don't be a smear on the side of the highway because you were too fucking cheap to ride safe.