This is the equivalent of "Exhibition Expert" in the base game. The exhibitions (or Hot Wheels Career races, as they're called in-game) in this DLC are split by performance class, starting from B and eventually working up to S2 class events. There are 28 routes in this DLC, including the Goliath route.
You do not have to earn the extra objectives or even win the races, completing them and earning just one medal is sufficient for this achievement.
Like the base game, you can shorten the race length through use of the blueprints. On the circuit races, you can cut down the amount of laps to just one. Switching to clear weather is also recommended, the tracks can get quite slippery when wet. In terms of the stunt pieces, the boost jump is the quickest to get by.
Adding me as a friend will make my blueprints show up in your game, if you want to save some extra time.