There are a few servers that run one combo for a long time, you just need to look for them. I would have suggested Redline, but they ban people for expressing opinions on an open forum, so it wouldn't suprise me if you were banned from there, I should know I used to be an admin on their servers before we fell out.
My suggestion is to learn a car, not the tracks, once you learn how a car will react to certain situations you will find it easier to learn the tracks. CTRA Single Seater 1 is a great server, the FBM can be quite user friendly with the correct setup, and it's good for learning tracks. You don't want a situation where you are only fast on one track.