Gems can also be acquired through mining.
As physical objects, Gems are a way to make long-distance payments from one side to another via Hat Magic.
 Proposed Canon
Rich sides may flaunt their wealth by encrusting Raiment and weapons with Gems and precious metals. Prince Creen of Delkey had his side's Moneymancer and Dollamancer stud his equipment this way.WB2014 Digdoug - Episode 6
Gems are the primary means of Shmuckers being hidden from a Moneymancer.
Gems are used in long term bribe ploys to lower a unit's loyalty when a turnamancer isn't avalible.