It depends what kind of bike you want. I always like the classic ones, and my fav. to ride was a Honda SuperCub (I can't remember what they're called here, Honda 90 I think?) -- they're unbreakable, cheap and the biggest selling vehicle in the world. I really like old machines though. They've constantly made them for decades, and you can even buy new licensed versions (china made) for almost nothing.
However it doesn't feel like a real MOTORBIKE. Most people go from the CBT to a Honda CB125, and there are loads out there. Some are really cool looking too (old and new).
I really like the old russian bikes too like the MINSK, although they're hard to come by.
Then again, I hate manual bikes because I feel like it makes 0 sense to have that much to do when you're basically sitting on a rocket. My fav. modern bike (which is cheap) is the SH125 is technically a bike but looks like a scooter. Such a smooth ride and it's effortless to operate.
If I had unlimited money I'd go for the Vespa 946
Ultimately, although I love them. I'd advise against them because they're fucking insane.