There are many ways to collect more diamonds.
To get to the place where you can get diamonds for FREE, please follow these steps:
1. Tap on the Menu button at the top-left corner:
2. Tap on the Diamond button at the top area:
3. Now you have Diamonds page opened, you can tap on a cell to get more diamonds. Please choose a working cell, which has a button with a diamond and value inside.
P/S: One special way is to “Watch a video”. This way you can do multiple times, limited to 10 times per day.