Give your army better protection: Legions of Steel (constr3, earth 3)
destroy enemy armour : Destruction (alt4, earth 3).
These spells don't require gems and won't hurt your own army (like Rust of Mist would). Start with 2-3 Legions of Steel, followed by as many Destruction as needed and finish with ranged spells/weapons like Blade Wind (evo4, earth3) or archers which shouldn't hurt your own troops too much.
Fight in your dominion to get +1 to moral to avoid breaking.
No, I don't know whether this will work because I have the demo only
