General Information about the different Troops
Archers only get close enough to shoot then stop (this depends on their range, how far away they stop, and how many turns they waste moving), then everyone charges forward and rainbows for them. Warriors fight valiantly before dying, workers kinda stare blankly and die, cavalry charge at enemy archers/defenses and tear them to pieces, as do cataphracts, swordsmen run around waving their shields about hoping to KO someone before getting killed, pikemen go around and kill people and cavalry, and then your ballistae and archers just shoot anything that moves.
You'll need 250 of these guys to start an additional city.
They are your medium speed / medium load for transporting resources. Scouts are fast/low, workers are medium/medium and transporters are slow/heavy. Workers can serve a good purpose when you need medium speed for a not so light or heavy load and your transporters are busy collecting resources elsewhere.
They are not built as combatants, but if you stick them in front of your other units, they'll draw a round or two of fire from enemy archers, while your more valuable troops are advancing.
Note: Workers can be used as a meatshield unit, but as they die 5x faster than warriors, do less damage and take 2x as long to train, logic dictates that they were not designed as combatants. Workers can serve a good purpose when you need medium speed for a not so light or heavy load and your transporters are busy collecting resources elsewhere.
Of the infantry units, the pikemen are the second most powerful, balancing attack and defense with a slight preference for attack. They also receive a considerable bonus against cavalry. Pikemen are far from immortal though, and they can be wiped out with the use of archers, swordsmen and even warriors.
A single archer can kill two pikemen before they reach him. If your army of archers is at least half the size of the pikemen army, then it can win without taking any losses, so long as your troops fire well. A single swordsman can also kill a single pikeman, and an army of swordsmen can beat a slightly larger army of pikemen. Alternatively, recruit a horde of warriors. You can kill a single pikeman for roughly every six warriors in your army. Warriors are cheap and have a decent attack.
Cavalry are weak against pikemen. Do not send them against pikemen unless you have no other option. Even then, expect high casualities.