How I started was...

ZXR250 -> 1000cc sports

but since streetbikes are much more forgivable, I'm pretty sure you can safely start with the Duc.

Heck... I poison a fren and he bought his first bike 250cc scooter, then 3 months later a 800cc BMW, and now he have 4 superbikes. and He is 58 yrs old!

So just go ahead with your Duc, take some lesson, maybe an advance riding course (not required but you will get more enjoyment out of your bike).