Wisdom, Pathfinding, Logistics, Earth Magic, Air Magic, Water Magic - these are very useful skills, and I always try to take them.
Diplomacy - I take it, but not always.
Luck and Leadership - I take them if I'm playing as a warrior.
Mysticism and Intelligence - I think they are most suitable for mages, and I sometimes take them when playing as a mage.
Tactics - IMHO, why? Why arrange troops? We wait until the enemy army makes its move and then crush them all.
Archery, Attack, Defense, Resistance, Spell Power, Learning - IMHO, these are useless. I prefer the following scheme for them: Basic - 10%, Advanced - 25%, Expert - 50%.
Navigation and Necromancy - these are two skills that make sense depending on the map.
Ballistics, Artillery, First Aid - useless, as are Scouting, Keen Eye, and Literacy.
Wealth - useful if it's impossible to build a capitol in the castle.
And finally, Fire Magic - fire magic itself is too weak. The Earth Blast spell deals over 1000 damage, while the Inferno spell (fire) doesn't even deal 500 damage. Maybe the developers forgot to add a zero at the end, and other numbers in the other spells? Doesn't it seem that way to you?