Hi @forykw,
You can check the game rules by going to the Rules on the screen with Goblin (top right). There you can find the minimum and maximum amount that can exist in a bag.
Maxiumum amount of gems is 12 for your sack and 13 for Goblin's sack. Minimum is 2 for your sack and 1 for Goblin's sack.
Goblin Prince is High low cards based game.

I hope I helped you with my answer! :)