When I am playing Warhammer, one of the most successful tricks for me is to always concentrate on getting enough strength in my regiments. Usually I take double handed weapons or halberds to increase any units strength to 4 or 6. This makes a unit of regular soldiers able to hit any unit out there and even able to take down a monster with some luck. Further, they get nice minuses to armor save which allow them to get around the good saves of other units. Whenever I am building an army this is the first thing I try to find is a few core regiments which I can beef up in strength and build the rest of the army around.
Armor vs. Arrows
Too often I find armor to be ineffective. Light armor in particular often gives no save and even with a shield it can be less useful against a unit with a strength of 4. Thus, when I consider armoring my units I try to figure out what the armor is for. In most cases I decide it is only good against arrows. I only need armor if the unit is going to subjected to a large amount of missile fire. So if I move fast or skirmish or start in cover, armor is optional.
Unfortunately magic in Warhammer is a game for the many mages. As everyone takes a dispel scroll or 3 it is very hard to get a spell through unless you can cast a few spells. Thus, you need to either have a lot of winds of magic cards or cheaper spells. Perhaps the best way to do this is to take several Mages so you can hold more winds of magic cards. This is often cheaper than items which do the same thing.
Halberds and Two Weapons
Often in army construction, we become dazed by the magic items and make sure we build are characters with a nice pile of pretty items. What we forget is the cheap use of weapons to do the same thing. For example why give a character the Blade of Leaping Copper when a second weapon is 23 points cheaper, or the Sword of Might when a halberd is 18 points less. These are inexpensive ways of pumping up characters without using magic. Also, with a magic weapon, that is all you can have, while with other weapons you can still have a bow or pistol or whatever, thus further increasing the value of the character by taking advantage of their high BS.