Anyone can add to this but here's a few things for new players to take note. First some tips, them some etiquette.
Tips
Cars cost money. Money is gained by driving. Simple.
In Campaign you can choose between GT League, Driving School, Mission Challenge, Circuit Experience.
I'd do Circuit Experience first as it provides money. Mission Challenge and Driving School will give you free cars after various stages.
Every day you play the game, you will be given a free car, so long as you drive a minimum 26 miles.
Etiquette
There's a quick tutorial in the Sport section. It's a requirement before you're allowed to race online.
FG Etiquette
Don't be a cunt. That's all.
Ok...
If you bump an opponent unfairly and it costs them time, ideally you should slow down and wait for them.
Try not to dive bomb unless you are abreast or close enough to make it legit, then you are within your rights to try a pass.
Try your best not to ruin anyone's race.
We play tough but fair, its not GTA, even if your name is Mike.😁