Do what you think will make you happiest in the long run. If you make a mistake, try to learn from it. Here in the states, many people are slowing/shutting down for the winter in a month or two and that is a really good time to be patient and look for good deals. Being patient almost always pays off in the long run...

 

They don't sell 125cc dual sports in Europe?

 

I don't know what it's like to drive a car in Europe or if that is something you are doing now or will be doing soon, but here in the United States I think a teenager should have a year of experience driving a four wheel automobile on our roads before they use a motorcycle on the streets.

Being an experienced car driver on who is a bike that particular day lets you be more aware of the cars around you and predict their behavior.

 

I rode dirt bikes or off-road only trail bikes when I was a teenager but in my 20s even my middle 20s that's when I got a 250 cc Enduro bike that was both street legal and could go 70 mph but was primarily made for off-road use. I only used it on the roads occasionally and decided that if I were going to ride on the public streets regularly I should get a motorcycle made specifically for that job-- one that was heavier, more powerful, smoother riding, has much better lighting, and some on board storage for basic tools and stuff.

 

How about used one of these: Honda CR125 or NSR125, TM MX125, Yamaha YZ125, KTM 125SX, GasGas MC125, Husq TC125, Beta 125 RR, RM125, KX125.

Get 2nd set of wheels and street tyres and you have dual-sport enduro bike. How do they verify B license compatibility? Dyno test or just look up table of allowed vehicles?

Really cool one is Stark Varg with 15bhp mode. Then de-restrict it with app for full 89bhp!!! Only 118kg makes for FUN bike!!! Alas out of budget.