How many simulations do you show? It takes a lot of simulating to get the gems you need. From what I understand, it doesn’t matter how many you have won, only how many games that you personally simulated on your system. You can look at your achievements to see how many games you have simulated and the gems you earned. With over 500,000 simulations I received 3814 gems.
The post below gives some good details on how to maximize the gem farming from simulations.