I finally unlocked the trophy yesterday. Playing on PS4 here is what i did.
First of all you wanna make sure you don't lose any points as it is so hard to gain them.
When you're in the game make sure you prepare the connection to the internet by double tapping the PS button:
PS Double tap>Settings>Network>Top of the list (where you can switch the internet connection on and off). Then go back to the game with the double tap.
For the following scenarios when you have to quit you'll just hit double tap and disconnect from the internet while in the race! Then you go back to the game and the main menu. If you're in the main menu you reconnect to the internet. Be as fast as possible. You should not lose any points.
Finishing 3. or better in a lobby with 8 or more players gave me positive points all the time.
Lobby with less than 7 players>QUIT
If you don't get on the podium>QUIT
If you get too much damage >QUIT
Although i'm usually racing with no assists, i turned on traction control on medium, the abs and the race line on. As you won't get spun out that easily and you can simply brake later, what helps you in the first carnage curves of online racing.
As you won't lose any points you can slowly build up your score. Even if you're not the most experienced racer... at some time the luck will be yours and you'll finish strong and get some points.
This thing is really a learning curve and you'll get better and better at it.
Maybe this helps someone out.