In game you need to start out as quickly as possible with a military. As soon as you have it scout out the surrounding area (obviously! hopefully your mother didn't raise a dullard. Kidding kidding) Take as many indy lairs as possible. get as much of that black stuff out of the way as you can. In starting early you need to come to a balance between lairs and putting pressure on your enemy. As your economy is weaker than the other factions, you need to make this up by either getting as much gold and techs out of lairs as possible or by putting pressure on the enemy so he cant work up his superior economy. If done right you can actually have a greater economy than your nat, council or ceyah adversary.

The key is your one strength. That extra company limit. If at all possible (without completely destroying your economy) fill up all your slots. Footmen and engineers work well for this as they are both cheap and the easiest to maintain. If you can't afford to fill up all the slots, and you are in team play borrow a village from your ceyah buddy and fill it up with shades. they make a great addition to your footmen hordes =)

Use the carpentry guild along with the billet. this makes some pretty cheap footmen. though I am guilty of not using the billet as much. 96 gold! OUCH.

I've had several companies of footmen take out the 2 companies of mage infantry that everyone loves to see.

Remember that footmen are fast and can strike quick at enemy citys while your friends are attacking his main force.

As you can maintain greater numbers of weak troops that the other factions, I have often used this strategy when facing a force of superior units: I will split my footmen engineer force into two groups. One group will be poised on the edge of a ZOP. The other will be next to his main force. Ill engage both at the same time. Usually you can take the city before his big bad force can destroy the diversionary. Footmen are cheap to replace while his city, (that upkeeps that big bad force), is not. Try it out some time.

With royals I will often go footmen and engineers till the end of the game. Very rarely will I go with the ever popular infantry mage. This is for three reasons.
Number one that combo is slow.
Number two you cant support these guys as well as other factions.
Number three any other faction will destroy this combo with their superior support forces.
I know I keep harping on this but footmen are great units. USE THEM!

ELITES- OUCH boy are these expensive. However you are getting the fastest, strongest unit available in the game. Do not put any support with these guys as all it does is slow them down. believe it or not the individual cavalier is stronger than anything in the game. (Well in multiplayer that is.) These guys cost 12 iron and 12 mana to upkeep. That's a lot of cheese to spend on one unit so make sure you can afford them. Usually a ranger is a good idea to put with them. this makes them able to use their speed in any terrain.
USES- They have two uses that I will explain. The first is raiding. two companies of these guys will take enemy cities before he even can think of coming to the rescue. And once he does come? go to another area of the map. Don't stand up to him unless you think that force will not slow you down much.
Cavs are the psychological unit of the game. What player hasn't had cavs show up in his back field and say to himself. OH NO! Heh come on we've all been there. I digress. Use these guys to wreak havoc and take attention off your overburdened teammates.
The second use is for flanking. stay off to the side of your ally's main turtle force and once the enemy engages, sweep in behind him. take out the support (which with cavs will go fast) and you have his front line. Not only this but NOTHING should be able to escape from cavs. Don't let anything escape. Don't get me wrong you can use the cavs as a front line force and they will pound just about anything into the ground. However you are wasting their true strengths.

COMBO- As I usually go footmen in the beginning of the game I have my wood supply built up pretty high. When I do get cavs (which use Iron and mana) I don't let all that wood go to waste. I keep my footmen army up. Then I'll coordinate with my ally and will throw them into the forefront of my ally's troops. this will save his troops from being overworked and make the team push even farther. After all footmen are easy to replace.
Meanwhile my cavs are destroying his backfield.
If I chose to use the cavs as a flanking force Ill use the footmen as a raiding party to wreak havoc on undefended cities.

Lastly remember that whatever faction you use give him more to think about than one place on the map. If he has to think about two fronts plus building an economy chances are he's going to screw up at some point in the game.