It's hard to give a definitive answer to this question. I lean towards not leveling Wisdom, but too many mechanics have been added to give a clear answer, so I'll present my arguments for and against. In the comments, we can discuss different strategies used in actual gameplay.

The developers added an interesting update in the new Heroes installment. Previously, we had to level Wisdom to unlock higher-level spells, but in the new part, that's not necessary. Now there are two paths:

• Wisdom - unlocks access to higher-level spells of all magic schools at once
• Each magic school unlocks access to spells of its own school up to level 5

There are 5 magic schools in total, and their essence has changed significantly. It can be described roughly as follows:

Neutral School - cannot be leveled as a skill; it is mainly used on the adventure map, not in combat.

Arcane School - all battlefield manipulations, unit control, and support spells

Day Magic - buffs, enhancing your own army's stats and their attack and defense capabilities

Night Magic - debuffs, reducing the strength of attacking units and their attack and defense capabilities

Primal Magic - offensive spells focused on dealing damage.

Yes, we can note that learning a single magic school is no longer as satisfying as in Heroes III - there, within Earth Magic, there were neutral spells, buffs for your own, debuffs for enemies, and even offensive spells. Now, the division is functional. So, one point in favor of learning Wisdom, especially if the hero is a mage, and also building a level 5 Mage Guild while the hero learns 1-2 magic schools.

However, neutral spells are now available anyway - without magic schools or Wisdom; they are learned through Astrology points in the town.

Additionally, each spell's level is now increased separately. That is, it's no longer the magic school level that determines whether a spell affects all enemy creatures, but the spell's own level. There are four levels. Levels can be upgraded with Alchemical Dust, but also by studying the magic school, though not to level 4 - you can get a maximum of +2.

It's also worth noting that now there are not just 3 levels of each ability, but also additional abilities - they also provide significant advantages for learning individual abilities.

From the last point comes another - now there are synergies. That is, if one magic school is learned, there will be some additional benefit from learning an additional ability. This greatly influences the skill stack you should choose. And given the remaining randomness in their appearance, you'll have to adapt your choices from game to game.

So the balance is now completely different from Heroes III. There, we simply understood the ideal stack and worked towards it. In Olden Era, we should rather understand how much Alchemical Dust we have and how fast its income will be (since to some extent, a magic school is just a saving of Alchemical Dust), who our opponents are and what spell stack we need, as well as what map and creatures will be in our army.