Use the sound cue of when to start a race in addition to watching the on screen notification. Use the sounds to judge when the race will start, then tap and hold the accelerator immediately when it turns green.
Shifting
Release the accelerator before you tapping the up-shift icon. If you make a mistake you will lose speed.
Tournament tokens
Winning a race in Wimp mode will only result in one tournament token. Winning in Racer mode will reward you with three tournament tokens. Tournament tokens are used to enter tournaments with a half mile track and money prizes.