Nothing wrong with a 250 powerplant. It will take you down the road at legal speeds and get you where you're going with wonderful economy. If you dismount a 250cc at 55mph, the result will be precisely the same as dismounting a 650, 1100, 1900 at 55mph. So think about an MSF course and see how a 250 feels to you in practice?
What will eventually become your "ideal" two wheel ride will more likely depend on your mission profile (commuter, tourer, weekend warrior, etc), your physique (tall short, gangly compact, svelte, +size, etc) and your motorcycle budget. And as you haven't entered into the world of motorcycling, you might or might not find it to your liking. In short (too late
) what you want out of your bike depends totally upon you.
All the rest of us can do is offer opinions; in the final analysis, yours is the only one that counts
And welcome, eh?
PS- I put 5500 miles on a 250 Rebel commuting to work and it works just as well on 2 lane, 4 lane, major or blue highways. 65mpg average.