I usually go at least 2 blue books, because Sorcerer books have a low level spell that costs 20+? mana, and make the enemy's spells fizzle. I also like Death magic and Life Magic, although Life magic is a little strong. I also take channeller or whatever ability that makes it so spells always cost 1x mana no matter the range from your tower. Also, I think I've always played as a Myrran so I can be a Dark Elf. Even their spearmen are freakin awesome due to having a magic attack. Nightmares are just sick. They get so much magic power for their population, and you can easily conquer the dwarves for a huge gold bonus or the trolls for melee troops. Plus you only have to worry about one computer wizard (sometimes none) for a while if you start in Myrror and if you take and hold the towers they work as pretty effective chokepoints (at least against the computer)
My favorite hero was the witch, Morgana, who raised units she damaged more than 50% health as undead on your side after you win abattle. Non-Troll undead work great as garrisons. Undead Trolls benefit from being undead while still regenerating after battle (even if they get wiped out their unit will be back at full health afterwards, unless your whole army is destroyed, which makes them the perfect unit to charge city gates.)
Also, the last time I played I had an independant gameplay patch on it that seemed to improve the game quite a bit. I can't remember what it was called but it gave all the settlers swimming ability so the AI isn't hamstrung if they start on an island and does some other rebalancing for the races and magics.
The thing I always hated was expansionist opponents, because that tends to be he way I play also. I'd lose all my fame for destroying all their crappy Klackon cities to replace them with dwarves or dark elves. I always thought there should be a Klackon wizard portrait, because one of the non player wizards always chooses them in my games.
I wish someone would make MoM2.