I expected something bad, but this... I played creepy japanese eroge games with better tactical gameplay.
Please, do yourself a favor and just spam those scorching rays and fireballs. At first, they only kill a couple of gargoyles (still speeding up crusade fights by something like 600%), but after a few level ups of your general they delete entire stacks in a single turn. The crusade minigame is unplayable without those direct-damage spells.
There should be a recruitable general with Scorching Ray and Master of Maneuver (the "stone wizard" guy), pick him because those are both useful perks. The "black woman wizard" is also fine, since she has Scorching Ray and you can select Master of Maneuver later.