You probably want to stay under 600cc and stay away from the sportbikes if you haven't ridden since your old 100cc bike.
You haven't defined the use you have in mind (long highway trips / commute / plonking around the neighborhood) so my advice is a a long shot.
Take a look at the smaller displacement dual sport bikes. These get terrific mileage, are easy for a beginner, and the maintenance is simple. Take a look at the Kawasaki Super Sherpa or the Yamaha XT250.
Make sure also that you set aside some budget money for a good quality helmet, jacket, and gloves.
And if you haven't ridden in a while, take the Motorcycle Safety Foundation class - they offer a beginners class that's probably too basic if you already have a license, and an advanced class that's not really that advanced (not a track class!) but it offers a great refresher.
If the dual sport isn't your cup of tea, give us a better idea of your experience and intended uses and we can re-assess.
E90 335i 6 Speed MT
Alpine White, Terra, Aluminum trim