Easy store points!
Go through single player Nationals, and earn the Mils Mesas environment or enough points to purchase it. After getting this map, exit the mode that you are in, and go to single player. Choose the custom event option, then go to "Nationals". Select the Mils Mesas track. Set the play mode to "Single Play", laps to "10", and number of opponents to "0". The MX superclass vehicle is recommended, but you can use an ATV or normal MX. Start the race, and do not worry about time or anything else. Just do as many tricks as possible. Try Dingo Backflips+ and 360+ for quick points. You can get about 700,000 score points and 350,000 store points.