Auto-translated
1. Earth 2. Air 3. Water 4. Fire
Here, many wonderful advantages of all the aforementioned magic types have already been described (damn, it sounds a bit awkward, maybe "revealed," but that's not quite right either, maybe "highlighted," even worse, but let's leave it as is:D). In different situations, any of them can be decisive, but that's already a topic of tactics. Therefore, I have prioritized them based on the frequency of encountering and using specific spells. And this, of course, primarily refers to spells of level 1, then level 2, and so on. The extreme, perhaps not entirely successful, example of combining Armageddon + Fire Expert + the presence of fire-resistant units + the absence of such units, vulnerability/suppression spheres, and a Cloak of Resistance in the opponent is less common than the combination of conditions for using Clone.
And I'm also surprised that the cheapest combat spell (of course, with Water Expert) - Teleport - has been mentioned only a couple of times. It is especially relevant for fans of necromancy. At the beginning of the game, it is rarely available, but you can sometimes get it by chance. Then, immediately level up Water, and even Slow, Haste, and Forgetfulness take a backseat. Well, and at the end of the game, when the main task of the opponents is to prevent the skeleton army from participating in the battle, cast it 7 times (according to the number of enemy squads), and with a maximum cost of 21 mana, kill the enemy and replenish the skeleton army.