Uprgrading
It is unwise to massively favour any one particular area when upgrading your vehicle, look to Balance your upgrades evenly as all the attributes contribute to improving its perfomance.
Tricks
Performing tricks will reward you with bonus points in the form of coins. Remember though that if your head touches the ground your run is over.
Forward Drive
It is important that you remember to keep all four wheels on the ground as much as possible because all the time they are in the air you have no contact which means no forward drive, hence no acceleration.
To be succusseful in a Cup challenge you will need to try risky strategies that involve near-crashing and shortcuts if you hope to eke out a win.