Hi, off course the following is depending on your way of playing the game.
As a Warrior I have decided to max out order and chaos and take some items for +Mana. Order and chaos for maximum in Resurrect (you got it definately after the return of the Iquisitor sword to where you got the contract) and sacrifice (for gratis troops, together with resurrect, paladins, inquisitors and time back). If I have enough mana runes I also max. distorsion and take some Transmute.
My way of playing the warrior is everytime to use the rage point as endless mana source (untill turn 20). Use your dragon or the spell Calm rage to transform rage into mana. Together with inquisitors and paladins you can got easy no loss battles. [big difference to Paladin skill resurrect, then I use black Knigths, and only them]. So I try to got ~60 mana points due to items and non magic skill tree things.
Because I only use some of the spells, I never choose alchemy, because I got enough crystals by destroying artefacts, buying and digging (most important thing on hard and impossible I think: digg, digg, digg).