Forza Motorsport 6: Apex

The fastest way to get this badge is by driving 20 different cars.

You will have over 20 cars in garage by only finishing the 2-3 first races if you get 1st place on all 3.

Select Free Play
Select "Top Gear East Circuit" track.
No Divatars
Select 1 Lap.

Just finish the short track once with each car you haven't used. When it says gold badge is unlocked, go to your driver profile and equip this badge.

Note: It can take from a few minutes to 1 hour before the achievement unlocks.
This game is very slow at unlocking.