Auto-translated
I feel that no single school should be neglected ;=) each is good in specific cases.
Personally, I prefer a mage with Light and Chaos magic, although it's rarely possible to build one like that. Chaos Magic is probably the most preferable when levels are less than or equal to 20, which is often when final battles take place. With Wizard's Mark and Lords, you can fight quite well. The tactic is this: first, cast area-of-effect spells, then once the troops thin out, hit the enemy with Chaos + res if needed. Usually, the slowest and toughest (or those with high defense) are left at the end of the battle. Such a mage is effective against almost everyone; he just needs specific targeted Chaos spells (Earth Shock, Chain Lightning, etc.), which means you have to build the Magic Tower and Library early, which isn't ideal. It's much more reliable to take Summoning and Light—it might be boring, but it's... predictable 8-)
Personally, I prefer a mage with Light and Chaos magic, although it's rarely possible to build one like that. Chaos Magic is probably the most preferable when levels are less than or equal to 20, which is often when final battles take place. With Wizard's Mark and Lords, you can fight quite well. The tactic is this: first, cast area-of-effect spells, then once the troops thin out, hit the enemy with Chaos + res if needed. Usually, the slowest and toughest (or those with high defense) are left at the end of the battle. Such a mage is effective against almost everyone; he just needs specific targeted Chaos spells (Earth Shock, Chain Lightning, etc.), which means you have to build the Magic Tower and Library early, which isn't ideal. It's much more reliable to take Summoning and Light—it might be boring, but it's... predictable 8-)