You'll start off with many villagers outside the walls in the farm lands. This campaign can be tricky and overwhelming but it's not too hard. The red Spartas will invade your homeland with their large army of phalanx, archers and cavalry units.
Fortifying the walls from invading red army
You'll start off in the Iron with 100 food, 100 wood, 100 gold and 100 stone. Many villagers, Phalanx, archers, one cavalry unit, one horse archer unit. After beginning this campaign quickly evacuate all of your villagers from the farms since the red Sparta army will march up your city and destroy the farm fields. Also quickly send your transport ship to pick up the villagers.
While waiting for the transport ship, have the villagers chop trees inside the city, have them build a wall around the watch towers, but since you'll be short on stone, you'll have to travel to one of the small islands with stone, build a storage pit or town center and start mining stone and chopping trees for wood.
Also have your fishing boats fish for food and trade boats trade food for gold at the yellow Sparta dock which is south. You can get even more gold if you destroy your docks and build them up at the northwest end of the map. But make sure the enemies don't attack your vulnerable dock.
The red army will arrive and attack the walls and watch towers with phalanx, have your phalanx attack the enemy phalanx and hold them off until you can finish fortifying the walls and build some extra watch towers. You can now safely build up your food, wood and gold.
Taking back the 4 artifacts
You should now build up 2 priests and build a siege workshop, create many ballistas, archers, triremes and some transport ships. Then put your phalanx on the transport ships. Also have your Hero 12 cavalry and your horse archer get on the transport ship and start attacking the red enemies chase you.
Also attack the brown Aegina cavalry units to chase after you. Then get your horse archer and Hero 12 back on the ship and the watch towers, ballistas, archers should pick off the enemies attacking your walls. Continue doing this until the army units are reduced.
Due to a minor glitch in the game, 2 of the red phalanx will be stuck which is nothing to worry around and you can kill them easily with archers or ballistas.
Hunt down any remaining cavalry and archer units until there's no more to stand in your way. Now head on down Southwest and claim 4 artifacts and you should win the game.