Create a gallery grid with Essential Grid

Navigate to the "Gallery" tab in the admin menu and add some posts. Make sure that each post have a Featured Image and at least one "Gallery Category"

Then navigate to Ess. Grid -> Settings (button of the specific grid)

Click to enlarge

Then follow these steps:

1. Click the Source tab
2. Set "Post Types" to Gallery
3. Select the categories you would like to show
4. Save the grid

The posts are now added to the grid. You can display the grid on your website with the "Essential Grid" widget in the page builder.