I think there should be a flat reward for your bracket and then scaled rewards within.
So Bracket 1 awards ALL participants 500 gems
Ranks then award additonal gems:
1- 500+500= 1000
2- 400+500= 900
3- 350+ 500 = 850
4- 300+ 500 = 800
5- 250+ 500 = 750
6- 200+ 500 = 700
7- 150+ 500 = 650
8- 100+ 500 = 600
9- 50+ 500 = 550
10- 0 + 500 = 500
Then each Bracket can be tiered accordingly and there can be clear gains for WINNING your bracket as opposed to being in Bracket 2 and below and knowing your reward is the same regardless of placement. That is a big fail in the reward structure in my opinion.
Disclaimer: I in no way mean to say that my above example is balanced or accurate just an example. 