Ciao Alex! I'm quite new to GTS as well. What I've been doing is to participate in the daily races and try to keep it clean. Don't go kamikaze, don't push people off the track and try your best. Sometimes (quite a few) you'll be pushed off the track, many will be mistakes but a few will be idiots. Just ignore them, don't be one of them.
If you start with the above, speed and nice racing skills will build up by themselves!
