Well done
@Peter Salt ! I'm not sure whether you have experience of riding bikes IRL, but that's a great achievement. If your derriere is sore, it's worth investing in some decent cycling shorts and a good saddle.
If you've gone to the trouble of doing the Mountain Route, make sure that you've got the 'Everest' challenge selected, since you'll need this to be working towards the whizzy glowing Tron bike.
The best way to get drops is to ride with Dan Diesel, since you get an accelerated drop rate when you're close to a Pace Partner. The best things you can buy at an early stage are the Canyon Aeroad 2021 frame and the DT Swiss 62 wheels. After you've got those, you might want to work towards getting a TT frame (only if you ride TTs, though). Most of the items worth getting are level-locked such that you're bound to have enough drops by the time you get there; I'm only on L28 but I have 1,500,000 drops and nothing I want to spend them on.
To level-up as quickly as possible, ride each course once and once only - there's a big bonus for the first time you complete each course (effectively double points). Set your display to km, not miles. Always ride to the end of the next kilometre. If you ride up Alpe du Zwift or Mont Ventoux, do a U-turn at the top and get the free kilometres for freewheeling down.
However, NONE OF THIS REALLY MATTERS if you're not racing - riding the basic Zwift kit on the Mountain Route might take you 30s longer on a free-ride, but that's all. The in-game kit will not feel nicer, nor make you more powerful!