[Manuk]

Something I always tought but never do. follow your army with scouts sneaking carrying lots of gems. After every battle transfer some gems from your scouts to your mages. That way you control how many gems you spend each battle.
if you give them boots of flying you can use them to come and go for resupply.

Obvious: if you have too few priests and/or too many sacred units make those units hold and attack to give time to your priests to bless them all. (you can overcome this with divine blessing if you have a powerful priest).

I thought you were cainehill. you are not.