As already mentioned, there is the Gilera, but tbh that's the only one I know of. 50cc "sports" mopeds usually have 5 or 6 gears.
My advice is to wait until you are 17 and buy a proper 125cc motorcycle rather than waste money on a 50cc rich-kid's toy - unless you are a rich kid. I know a year is a long time to wait for a teen, but a 125 costs only fractionally more than a 50cc and has so much more power you won't believe the difference.
I would describe learning to ride a motorcycle with gears and a clutch as "complicated and difficult for two hours". That is to say, when you do the CBT (compulsory basic training) you'll struggle when you first get on the bike, but then the technique will just *click* and you'll be changing up and down the gears without even thinking about it.
Be warned that getting into motorcycles is expensive, it's not just the cost of the bike you have to worry about, it's the insurance - which will be very expensive for the first year or two. There are plenty of 125cc motorcycles to choose from, I'd recommend any modern Japanese bike (but not Chinese) and two of the most popular are the Honda CBF 125 and the Yamaha YBR 125.