Monster Jam: Path of Destruction

Hard difficult can be a challenge to some so leave playing on hard until you have faster trucks and upgrades unlocked, after selecting an event you chose your difficulty.

Win gold on 20 events and this will pop, stadium races are the quickest whilst stunt challenges, gate rush and freestyle events are the simplest.

I suggest doing all 8 stunt challenges along with stadium races and the remainder with gate rushes for your 20.

Here is a list of the 20 events i achieved gold on at hard difficulty using Custom Monster Truck 14:
Minneapolis
Stunt Challenge 1
Stadium Racing
Stunt Challenge 3
Gate Rush
Indianapolis
Stadium Racing
Gate Rush
New Orleans
Stunt Challenge 6
Stunt Challenge 8
Gate Rush
Stadium Racing
Orlando
Stadium Racing
Stunt Challenge 5
Stunt Challenge 7
Gate Rush
Houston
Stunt Challenge 2
Stadium Racing
San Diego
Stadium Racing
Time Crunch
Oakland
Gate Rush
Stadium Racing

Wait until you have unlocked better trucks and upgrades for the trucks. Upgrades are automatically applied to all the trucks when you get them. The easiest events are the Stunt Challenges. There are 8 of them. The Stadium Racing events are good too. They are very short and not too difficult with an upgraded truck. If you are having difficulties try the Team Racing events and hope your teams combined score is enough to win.