Wisdom, Pathfinding, Logistics, Earth Magic, Air Magic, Water Magic

I try to take Earth and Air, Water or Fire – if the first two don't work out. I prefer Pathfinding to Logistics if I have a choice.

Luck and Leadership – I take them if I'm playing a Warrior

I don't take Luck, Leadership – only in combination with Diplomacy ;)

Mysticism and Intelligence

I never take them.

Tactics – IMHO, why? Why arrange troops? We wait until the enemy army makes its move and then crush everyone as needed.

With an offensive tactic, this skill is useful to quickly reach the enemy with all forces; with a defensive tactic, it is useful to prepare well for his attack. So in any case, it is extremely useful.

Archery, Attack, Armor, Resistance, Magic, Learning

Archery – only for a Tower. Attack – essential for any attacking Castle, also useful for defensive ones. Armor – essential for any defensive Castle, not superfluous for an attacking one. I haven't found a use for Resistance, maybe I'm wrong. Magic – is this witchcraft? Definitely useless, that's right. Learning is also not very useful, unfortunately.

Navigation and Necromancy

I don't take Navigation, but upgrading Necromancy is a must.

Ballistics, Artillery, First Aid

If there are many Castles on the map, Ballistics will be useful. I don't take Artillery myself, but I can't say that it's a bad skill; you just need to know how to use it. The same goes for the Tent.

Scouting, Keen Eye, and Literacy

You can give Scouting to a secondary hero. Keen Eye – is this eagle eye? Well, yes, it's practically useless in the third game. Literacy, if I understand correctly what we're talking about, is suitable for a secondary hero.

Wealth

Treasury in my translation. I don't take it for the main hero, but for secondary heroes, it's a skill of primary necessity on any map.