Please offer some advice.

The main target in battle is the hero. He should be eliminated first, if possible. Ideally, combine magic X (some kind of magic) with chaos magic to deliver a devastating blow to the hero. And when the enemy sees that you have chaos skills, they will position their troops in a "standard" formation, which exposes the hero. Try to achieve high morale. This can be achieved by combining Warfare with Tactics to create a general (+1 to morale for ALL your units!). And the first turn can be decisive... Initiative is very important. So, try it out... :)