The game has now introduced a slot machine which you can spin every hour (cooldown timer which you can finish by using gems) this gives you a track to complete without any faults.
When you have completed the track you then get a turn at the slot machine for prizes which range from coins to gems.
The game does have quite a few in-app purchases but I've not felt the need yet to purchase any. My current fuel meter is 35 which gives me the chance to play seven tracks. After this I leave the game alone & come back later when it has been refilled.
I'm currently trying to get the last piece to unlock the Jackal bike. But Butch just pips me to the line, I need to try a better line through the track with a few tricks to get a better landing.