For a first bike I would keep it small but not so small you’d be bored or embarrassed to be seen on it within a few months of riding it. You’re not a teenager ya know.
I would advise a road bike rather than duel purpose and a sport rather than cruiser. These are much more fun on the road, very easy to work on and when you are bored with it great to modify. Think “Café Racer”, very hip at the moment and I know how important that is to you...
I’m a Honda guy so I’d look for 1968-74 CB450, the way cool ’89-90 GB500 (very hard to find), ’72- ’74 CB 500, ’74-’78 CB550. If I could find a deal on one of these I’d buy one today just to f@ck around on.
I had a ’78 CB750F back in the day;
…a very fun bike but a bit of a pig and more than you want or need.
I know there are some nice Yamahas out there but don’t follow them like I do Hondas. Kaw’s and Suk’s I don’t really care for…that’s just me. I know nothing about Beemers and will not comment except to say they were never for me.
Let me know what you get.