Do your army units "level up"?
 

I couldnt find any mention of this in the manual and couldnt find any indication of such when I clicked on a unit (I would have expected a bar to indicate bumber of points needed for the next level). I am a level 6 mage and dont seem strong at all. I keep buying new units but this is hampering my ability to raise a significant amount of gold needed for a quest. If the units do indeed level up, perhaps I should have spent more effort keeping them alive.

Thanks for any tips!

No, units don't "level-up". Only hero does.

I was able to upgrade my priests to a higher level. But i think that's the only one.

yeap you can upgrade them to inqs but not because of battle experience gained by unit but by special skill you learned.