Start with the two official patches, then get your wheel setup and working nicely in the game. Go through the whole rally school and try to master all of the lessons first. Then hit the stages.
I personally only run with new cars installed, and the odd texture pack. Tried RSRBR and didn't like it simply because of the interface, it just wasn't worth it to me; and all the user-made stages I've seen in the past looked pretty piss-poor anyways, but I've been out of it for a while.
WARNING: Do the rally school lessons BEFORE installing mods. ESPECIALLY any new car overtop of the default car (2001 Subaru I believe?) as this will either cause the lessons to crash or the car will be undriveable due to mis-matched physics files. New cars should be fine in normal stages/rally season/challenges, just not in the lessons.