First off, I really suck at driving games, but even so, there are still players out there that occasionally have worse days than me. Finding them is how I got this. If you don't have a buddy to boost this with, keep signing out of sessions with good players and you will eventually find someone who are new to the game. Find a type of car and a track you feel comfortable with (e.g. 4WD in England), and keep voting for an option with one or preferably both of these.This will, of course, help you get an edge over the players even newer to this than yourself.
I started playing online today after getting the 1000 miles in career mode achievement, and the first races were on tracks I haven't driven on in a long time. After I logged out of this session (with one guy that constantly beat me with 20 + seconds), I found myself alone in a session, voted for a track and a car I felt OK with, and suddenly there were two other guys in the session. They were probably new, as they didn't even vote, and I soon got both this and the hill climb win achievement. As Earlydaze says in his solution, the online for this game is nearly dead, so there are not many sessions to choose from.