Seeing you already are S2 licenced, it did not take you long to decide! Thumbs up!
As Mille pointed out, the online racing is time dependant. Best way to find a server that suits you is to try couple of them out. Hop on, do some races, talk to the racers and switch servers if you don't like it. If you do this for a while you will get stuck on one or two servers sooner or later.
Many teams also have weekly events you can take part in once you have been on their public servers for a while. Those races provide decent racing without any crashfests.
Don't get frustated if you get crashed out several times in a row, though. It happens almost everywhere on public servers. Learn to avoid especially Lap 1 Turn 1 Mayhems.
As to you question about additional Tracks: There are none.
LFS offers several Configurations of the tracks included that should keep you busy a while. Modding is not officially allowed and I am not aware of any tracks made for LFS.
I started to switch reality for LFS, so Blackwood, South City and such are the real racing tracks for me nowadays and Laguna Seca, Silverstone etc. are the fantasy ones, they only exist in this awkward game called "real life". I heard the graphics are good, but everything else...
