Hand of Fate. Part 2: Despair

Question: How to capture the first Castle with minimal losses? I do this on the 2nd week, but during the capture, all the mages, half of the Goblins, and some Djinns are killed (there is no difference between Hero and Veteran difficulty, only more money is given at the beginning). And how to get the Cold spell at the beginning? There are no Sorcerers to buy it from, and the chance of it appearing in the Mage Guild treasure chest on the way to the Castle is small, plus the losses are high. Who uses what tactics to replenish losses (again, at the beginning, 1-3 weeks)? I think I wasted my time developing Light Magic; the spells still can't be bought right away. Maybe it would have been better to develop Mechanics (and the Castle would be easier to storm), developing the Ballista and Tent? Also, how to increase the chance of getting the Education artifact at the beginning? I barely manage to get it by using a Mentor and spending all my money, which is unacceptable. With this many enemies, it is definitely needed. Added 8 minutes later From the very beginning, I develop Chaos (Cold - Freezing Cold) + Logistics (Difficult Terrain). What is better to develop as the third skill (1-2 weeks)?