[Edi]

The gem income from mines is not that straightforward. Coal mines provide 1-2 gems. I don't think I've ever seen a coal mine provide 3. Iron mines, silver mines and gold streams all provide 1-4 gems, with 1 and 2 gems being most common, 3 being rare and 4 being very rare. There are some special sites that also provide gems, but just two so far that I remember.

As far as non-mage rituals, the Pirest King's Tribal King commanders can slave hunt. The Burgmeister can turn farms into Hoburg villages (goes from 1 gold to 3 gold and 1 weed) and baron and high lord can raise levies.

Everything else ritual wise is by mages or other special commanders, but mercenary mages are available for hire for everyone. Many classes have class specific special mages in addition to the standard list.