Just a heads up most games developers take advantage of the free announcement and advertising system in place on Xbox Live. The game developers post a variety of items from upcoming updates, recent additions, patch notes, community events, special weekend offerings, whatever, etc.
It should be very easy to get control over your own ‘Game Hub’ to do this. You could post info at the same time you put out a twitter announcement or blog post. This could help increase the awareness of Gems on Xbox to potential new players (or have existing players return to the game if they see something new/interesting).