I can be rolling in piles of different gem types, but always seem to be running short on death gems. I spend them almost as quick as they come in.  I also tend to (almost) always have at least 3 levels of death magic on my pretender regardless of the nation that I am playing.  
 
I typically summon mound fiends to help with spending the death gems.  Skull Face, Skull Staff, Standard of the Damned, Wraith Sword, Horror Helmet, Skull Mentors, to name a few items.  If there are any gems left over they go to summons. 
