If the global slots have not been filled, cast a mininum gems global. (So if the global normally costs 30 gems, with a 20% reduction it would be 24).
Apart from that cast the ritual spells, iirc hidden in snow is in enchantment. Hidden in snow gives pretty good mages/undead, and even better if they are cheaper.
Many of deaths summons are enchantments. If you are playing MA Agartha, than it is time to win the game!
But when I see a province like that, it gets a lab automatically, and if it isn't that bad a position, or if it is near my border, temple and a fort!
Alot of the major gemgen spells are in enchantment, from Eternal Pyre to Arcane Nexus. If your an air nation, 3 gem seeking arrows instead of 4. Lots of death summons and goodies like Gargoyles to be had.