At each Level increase, you will receive a Coin Reward as well as unlocking new items. From Level 1 through Level 10, a Level gain will give you a Reward of 200 Coins. From Level 11 through Level 20, a Level gain will give you a Reward of 400 Coins. I was very pleased to discover that, from Level 21 through Level 30, a Level gain will give you a Reward of 600 Coins. As I have not reached Level 31 yet (nor even Level 30 for that matter), I cannot confirm that any Level gain between Level 31 through Level 40 will give you a Reward of 800 Coins but I daresay this is the case. The highest Level that can be achieved at present appears to be Level 70. I would imagine that the Reward for any Level Gain at higher Levels would be as follows:
Level 31 through Level 40: 800 Coins
Level 41 through Level 50: 1000 Coins
Level 51 through Level 60: 1200 Coins
Level 61 through Level 70: 1400 Coins
I would love to have actual confirmation of these higher Rewards from any Player who actually has reached any Level above Level 40.