First newbie game: first impressions!!!

[lillumultipass]

I have started my second game Last night, with Machaka, I took a Great enchantress with 2 in most magic paths (all but blood and water I think...), and 6 in astral...to have a site searcher...anyway, it's strange to have normal units after having used gian with Jotuhneim; I actuallay lost some battles!!! But one was very surprising: I had my pretender, a black sorcerer, I had lost of animals (through the spell), horned serpents, a wyvern, and a few archers, and machaka warriors, and I lost! I was facing something like 25 crossbowmen and 15 heavy infantry with a commander...and I watched the replay, and I saw that during the battle, my pretender, that was supposed to cast spell, just came forward into the melee to get slaughtered...I don't understand why...
I find it hard to know when I have enough firepower to win a battle...with Jotunheim I knew I could win all battles versus independents...but here...