Solid Gold Achievement
Achieve a gold trophy in every single race in the Event list in Season Play mode.
This is the most time consuming in the game. You need to finish 220 events in 1st place, and every event consists of 3 or more different tracks.
The fastest way is to hire a driver compete the race for you. He will take 50% of the winnings and you won't be able to earn any XP, but this way you don't actually have to race. You can just set the race up and then go do something else until the race is finished.