What do the different types of in-game currency buy?

Coins

Coins are used to pay the entry fee to certain events, to build or upgrade vehicles, and to purchase boosters before a race. They are also used to purchase better quality parts from the Coin Mall.

Coupons

Coupons are used to purchase parts. When you purchase with coupons you will receive a part that has a star rating between 1 to 5 Stars.

Clovers

Clovers are also used to purchase parts. When you make a purchase using a clover + coupons you will increase your chance of receiving a part that has a star rating between 3 to 5 Stars.

Trophies

Trophies are premium currency and can be used to purchase higher quality parts. When you purchase with trophies you are guaranteed to receive a part that has a star rating between 3 to 5 Stars.

When you use trophies in the Choro Q or KIA shop you are guaranteed to receive a part that has a star rating between 3 to 5 Stars with the chance of it being Choro Q or KIA.

Lucky Diamonds

Every time you use trophies to buy parts you will receive 1 Lucky Diamond. When you have 7 Lucky Diamonds, the next time you purchase with trophies will guarantee you a 4 to 5 star part.

Scout for Team Members

Trophies are also used to scout for new team members (scouting for team members gives you bonus coins).