This unofficial Warhammer: Mark of Chaos game guide contains a walkthrough of all available missions of the Imperial and Chaos campaigns. Description of each mission contains helpful info on gaining advantage over the other fraction and completing received goals. The guide also offers additional info on heroes and their units.
Few years ago I played Warhammer Fantasy Battle, particularly Chaos Warriors. Because of that I think that quality is better then quantity, so in every single camp I rather upgraded higher level units then bought new ones. Sergeants are most important, musicians and bannerbearers are needed only when your troops have weak morale (especially Skaven). I tried to buy best weapons and armour possible, but when I didn't have enough money I were buying only weapons for shooters.
Best Video Game Guides by http://guides.gamepressure.com/