Koinon Hellenon

Early game difficulty: medium
Mid game difficulty: easy
Late game difficulty: easy

Army/unit

KH has only one unique unit: the Epilektoi Hoplitai... and that's all they need. Epilektoi Hoplitai as mentioned by other posters are FAR too available after you've fully completed the KH reforms and built the top level government everywhere. With TWO per settlement you can pump out enough to form entire battle lines of elites. Imagine having phalanxes of Hypaspistai at your disposal.

You should also be aware of the Hoplitai Lakonikai which are available to any Hellenistic faction after the Spartan Agiad Reforms, a reform that the human KH player can trigger more easily. That unit is somehow even weaker than standard Hoplitai, with less armor and morale. "Upholders of ancient spartan military tradition" my butt. Still, they have a cool looking skin and are a rare treasure for the roleplayer.

At the beginning of the campaign you have very little cavalry, so a traditional hammer-and-anvil tactic is much more difficult to accomplish. Adopt a Battle of Marathon tactical doctrine and have a spread out and bare-minimum center with stronger flanks comprised of the rest of your infantry and all your cavalry. Use the flank infantry to challenge the opposing cavalry while your Kretikoi Toxotai assassinate the enemy general. Meanwhile, your meagre cavalry should be able to launch carefully timed rear attacks. Your Classical Hoplites are very tough for "generic" infantry, and will grind down the opposition regardless of what happens.

Campaign

At the start of the campaign KH is in a state of disarray. Two fleets have desperately sailed to Alexandria and Pantikapaion in a plea for aid, but it fell on deaf ears. Move those failed emissaries back to friendly docks to be scuttled, save for one ship from the fleet at Alexandria. A huge party of KH nobles are scattered around Athens. Move them all as well as some Epilektoi Hoplitai to Sparta to help repel Pyrrhus. Your faction leader is in Crete with a small crack team of elite troops. Bolster their numbers with even more mercenaries, which MUST include some Thessalian Cavalry, and beseige Knossos.

You must win the siege battle at Sparta whether it's against Pyrrhus and his royal army or one of his generals leading a mob of crap troops. In either case the surviving army would piss off towards Aetolia, leaving only the Makedonians as your foe. Once Crete has been pacified, use your lone fleet of Triremes from Alexandria to transport the FL and his elite squadron to Sparta. Congratulations, you now command a full stack of nothing but infantry and a bunch of Thessalians (and that weird FM with an Hippeis bodyguard). Conquer Korinthos to acquire your second Metropoleis, and after the devastation heals you should be making a small profit.

As leader of the emergent fellowship of Greeks, you have two reforms to complete: the KH reforms, and the Agiad reforms. The pdf guide explains how to achieve the former much better than I can, while the latter is accomplished through builting level 4 farms in Sparta, which requires a City level of development. Things to note about the KH reform process: Don't try to snag Syracuse or challenge Pergamon for your 3rd Metropoleis - conquer the City-level Thermon or Pella instead and build a Market followed by a Metropoleis instead. Or wait for Sparta or Rhodes to develop. Also, when building the unique buildings for some of the steps, DO NOT dequeue them once queued. The script would break and you'd have to wait till turn 400 for the fallback to occur.

With a fully reformed KH you can finally train that 1 General 19 Epilektoi Hoplitai stack you've been dreaming of. Put off finishing off Epeiros or Makedonia as QS suggests if you want a more formidable final boss. In that case, your avenues of expansion include Asia Minor and Sicily. The former is immensely rich and provides fantastic heavy infantry and cavalry, while the latter requires much more investment to maintain due to Carthaginian presence, but offers a diverse selection of western Mediterranean mercenaries.

You should rectify your cavalry shortage by hiring Thessalikoi Hippeis and Raskumezenai before the other Hellas factions do, as well as hog all the Cretans you can for elite light infantry and missile infantry. This will result in a more well-balanced force than that homogenous monstrosity.