In the final battle of the Good Campaign, six or seven Ballista towers
will help to kill the Balrog quickly. You can gain more ore and food
points by bulding a Stronghold, Mill and Foundry in the small camp just to the west of the main camp, but make sure you have a couple of Ballista towers and at least one Ranger, as well as a few invisible Elves.
You will also need to claim the Claw of Protection to the Southwest, of course.