As mentioned before, you will have to start with the compulsory troops, which together with the General, hero(s) and a magician will tie up app 50% of your first 1000 points.
The Empire army is definitly a combined-forces army, although you could opt to go "with lots of knights" (an approach some players take because 1) you have few units to paint 2) Cavalry is a good buy for any WM-f army), as soon as a table has a good Warmaster-quantity of terrain your mixed set-up will out-perform the knights every time.
You do not have über"-troops, but when used in conjunction with each other you should have a fighting chance against most opponents. As mentioned your knights are the unit with the most "punch", either charge them ahead, and have them die gloriously, taking out half the opponents battlelines and winning you the game

, or combine them with some Pistoliers and explotre them as a flanking force, or mobile reserve.
For flanking your pistoliers are worth every penny. Against most armies you will be able to have the "longer" battleline, so the abilty to bring them around a flank and shoot away support, or to backstop and destroy units is well worth a try.
Dont put your money on the "shooty" units. Shooting is Warmaster is seldomly enough to kill units outright. Your shooting units do have one important task! If properly applied shooting will disrubt battlelines, breaking them up in smaller "formations" and single units. Which will force your opponent to issue more commands, which means a bigger chance for failure and thus loss of initiative. Or "snipping away" stands from units, reducing their fighting effectivness and imposing additional command penalties!
Important note on shooting is that your hits are applied on a unit imidiatly when they exceed the hits of a stand. As you can decide the order in which you work through your shooters, this mechanism allows you eg. to snip away a stand from a screening unit, which would be the nearest target for your cannons, bringing a more opportune target into the cannons field of fire. Also, when shooting at units that are partly in cover you would direct attacks on the stand in the open first (without modifiers), before moving to the defended other stands.
And remember that you normaly shoot with all stands of your unit on the SAME target, unless a stand can not make LOS on that target, in which case it shoots ar the nearest target in it own LOS
Your artillery essentialy has the same function as the normal missile troops, but through its longer range, no AST and bounce effect has even a bigger disruptive impact when applied correctly. Find a "fire corridor" to set-up in, and 9 out of 10 times your enemy will avoid crossing that, which means that you can "dictate" your opponents options (which is what Sun Tze tells us wins battles

). BTW realize that your opponent will probably make the arty a priority target, and with most armies having access to flyers (the one "arm" you dont have) be aware for "death from above".