Here is a basic explanation of the prize system in the Arena. 

1. If you exceed your previous highest ranking, you will receive a one-time prize.  You will have to continue to improve your personal-best ranking in order to keep receiving this type of prize. (See detailed rules by clicking "i" in the Sky Arena.) 

 

2. Every night at 9 pm ranking awards will be sent to players based on their ranking at that time.