The story so far with Armenia...

Plan: Head for Pantikapaion, conquering Kotais on the way so I'd have supplies. Spend nothing on native cities. Keep Armavir for mining revenue but no real effort to defend it. Maybe give it to third party if Seleucids look like attacking it.

272:
- Taxes -> max
- Expecting mainly sieges in near future, disband medium cavalry + HAs + skirmishers
- Take Kotais in autumn. Missiles push them back, ram breaks gate, spears hold main street, slingers fire over their heads at the square, cataphracts go round the houses to charge defenders from sides/behind. These are my normal siege tactics.
- Leave 1 unit, buy mil gov for 5% happiness to get higher tax.
- Build a few slingers at Armavir, cheap on the march and handy for sieges.
- Ceasfire with Sauromatae, who will be my new neighbours.

271:
- Spy killed on 92% mission, grr... Use diplomat to watch enemy troop movements.
- Long march by the sea shore for main migration army.
- Great horde of Eleutheroi skirmishers from Trapezous besiege Kotais. Sell buildings. Disband garrison, the more Eleutheroi survive the "assault" the more trouble they'll make for somebody else.

270:
- Marching still.
- My main army fights the Eleutheroi field army east of Pantikapaion. Missile infantry beat their HAs, cataphracts smash everything else and punish HAs for coming close when they're out of ammo, spears protect my missile units and do some pins or flank their engaged horses.

269:
- Besiege and take Pantikapaion (stone walls). Goes OK. Sappers break wall, cataphracts blast a way though it for the rest, then usual tactics.
- Put in type 2 gov. Type 1 not avalible, 2 gives level 3 local MIC which does all I want. Higher MIC just gives some elite Skythian cavalry which I don't need. I usually avoid elite units, they're an admin headache.
- Faction leader dies. Bye-bye 50 cataphracts. Been rejecting loads of awful family members, not quite sure why since I'll just use them as cavalry but never mind.

268:
- Settle a bit, get some money.
- Manoeuvre on strategic map to catch Chersonesos field army away from town and hit them down a steep hill. Big dangerous enemy, heroic victory.

267:
- Very tough siege of Chersonesos (stone walls), using 50% mercs. Can't sap so I have to take the walls. Close and bloody battle in which I lose a spear unit in a burning siege tower, but I get the gates open and the cataphracts blast a way for the others. About twice my usual losses. Good thing I hired the classical hoplite mercs to go with my wimpy spearmen.
- Install type 2 gov, and have arest.

266-265:
- Good income allows continuos construction. 3 cities including 1 mine, and not much military still alive. Get morale, population, culture all going the right way.
- Get a local MIC going in case of need, but relying on mercs and generals to avoid recruiting out of population. Cities are <2000, need to grow.

264:
- Message right out of left field says I'm at war with the Sauromatae. I also seem to own Kotais for some reason, and it's got 10 spear units inside. I figure the Sauromatae took it without me seeing, and it rebelled from them to me. So I disband all the units (which were costing 2000/turn) and let them have it back.
- Sauromatae won't make peace now, since we've got two land frontiers. I think of offering Armavir for peace, but it brings in 700/turn and I can take the Sauromatae. I'd give it up to avoud trouble with Big Grey, but not the horse worriers.
- Take out the Olbia field army in weird river battle where they have all the misssile troops but I flank them with cataphracts via two fords.
- Take Olbia, wooden walls, not so hard as the last two. Has to be type 3/4 gov, I prefer 4 (better happiness).

263:
- Wander east and take Tanais. No walls, five defending units. I find Sauromatae buildings inside and their leader watched the siege from over the river. I've probably just annoyed them. I put in a type 2 gov.

So I now have four cities along the north of the Black Sea, and a recruitment roster that's better than I'd get in my homelands. My problematic neighbours are the Sauromatae, who are a lot softer than the Seleucids. There are plenty of lightly armoured barbarian infantry types to the west, who'd be east meat for my cataphract/missile/hoplite army.

The only problem is that I'm playing Armenia who don't have much of a tech tree (doctors, paved roads etc) and they'll never amount to anything.

It seems migration is feasible, but it makes most sense when you didn't have much to lose by leaving regions 1/2. You'd need a good reason, like avoiding the Seleucids. Armenia were ideal.