Here's my current goals...
All Gold
All Arcade
All Time Trials
100% Wins
Use purchased cars *whenever* possible
Purchase cars inefficiently (don't rely on cars that can do a lot of races)
Don't use "NA Tune" or "Turbo" mods whenever possible
Complete each league in order by license
Try to keep all races competitive (win by 10 seconds or less)
I'm currently just shy of 80% complete and still maintaining my mandate. It's a lot harder than you might think because you can't use those wonderful Camaro Race Cars or Vertigo Race Cars one series into Amateur League. You also don't automatically have the funds to max out the upgrades on a car because you have to buy so many.
Professional League is breaking my "win by 10 seconds" rule, though. Because the races are so long, it's too easy to win by a lot. May have to amend that somehow to exclude the Pro League or something...
Anyway, give it a shot. It's a very competitive game and a little more in depth. It also made me try to get more out of my settings than I did before.