The way GEMS are managed in Manila isn't too flexible. Here's an addedValues solution which improves upon it. It consists a single group which can be imported to add the functionality to any Manila website (with addedValues installed and enabled). That's a 3 step process
There are no Gems.
To have this page replace the normal Manila Gems page; assign a url to this page. Now go to the addedValues preferences page and enter the full url in the Manila Override URLS table entry called editorialGems.