Reaping the Rewards - Forza Horizon 4

Complete a race of 3 or more laps at The Goliath in a Forza Edition Car - 20

Firstly, you will need to unlock Level 20 in the Road Racing Series, the best way to do this is by completing the The Colossus Road Racing Series Event in a Forza Edition Car multiple times. Doing this will grant you between 10,000 - 15,000 Influence Points. Once you have unlock the The Goliath Event, create a Blueprint or select a previously made Blueprint Event with 3 or more laps on it. Then complete the race with any Forza Edition Car you own.

This is a reference to the developer's believing that this would be where most of the grinding of experience would occur. Completing the race in a Forza Edition Car is one the fastest ways of gaining experience in the game.

Aston Martin Vulcan - 2016