A small guide for under 30 days:
First buy tires, then fuel, then concentrate on buying prop and eng, transmission. After a complete upgrade of the sportscar keep driving it until you hit 2500 in cash. Then buy the Schoolbus and of you go!
Very ez badge. In the 3rd chapter there is a shortcut in the beginning. Just after entering the water and hanging on the plants you can jump the whole way down and enter at a checkpoint. You will just make it in time for normal air if you just run further :D
Congratulations! You just won the White Rushin' Badge and 30 points!
173k points in points mode. Trick is to use the Beserk option a lot in combination with the time lapse. So use beserk for the real hard moments and stall the time after it to get a fast recharge. Good luck!