I would suggest the following locations and founding order:
1. River city SE of Seoul: close by = low cost, it can build an obelisk (or whatever they are called in warlords), working unimproved happies (good mix of food, prod and coin) and produce a worker to work the sheep later.
2. Coast north of Seoul: also low cost, high early growth potential. Once you have a worker, you can chop for the obelisk, then get a workboat out for the clam, improve the wheat and pump workers and settlers here.
Make sure you have some four or five warriors by the time these cities are founded, they can garrison your cities, fogbust sw and e of capital and thus keep more than half of your island lit up.
3. Fish and rice city in the far east, on the circle, or even on se hill a bit expensive, but can chop and get high food quickly. With 7 warriors, you can now suppress barbs on two thirds of your island.
4. Desert city, 1n of desert tile (turquoise cross) see the beauty in founding on desert, but would want more overlap with northern cities, which can all work coast. This site could make for a good capital later, reducing maintenance cost to all cities.
After this, it doesnt much matter. You might want to found sw of Seoul, which also gets you the third naval health-bonus; should take care of all your coastal/harbour cities.
Consider putting three, not just two more cities on the northern coast; if you found #3 se of your planed location, you can fit them in with acceptable overlap. Start with the cow, then one for wine once monarchy is online, the commerce from this tile should make the city viable. Your goal should be nine or so cities in time for caravels.
Some other notes:
Scout the south soon, there may be silver, bronze or iron down there, which could make for a prio 3 site.
Also, check every corner of the island to see whether there isnt some sort of sea-link to another island / continent. Sometimes it pays to settle the furthest points of an island (i.e. the desert w of capital) so that when the city pops its borders, you can see across the sea and, with some luck, get a boat across. Cities on opposing shores can bridge a four seasquare gap and get in contact before caravels, which would get you a trading partner and improve your chances in this game hugely.
In terms of barbbusting, I would start spawning warriors soon, and hope for horses. If you dont get any, I would still suggest bypassing archery (unless this is immortal or raging barbs) and use even more warriors to get maximum fog suppression. This should see you through to iron working and save you techcost needed for optics. Plus, the warriors will make good stationary units for your cities later.
Provided you really have no early happies, so your strategy should be to grow in number of cities, which in turn necessitates cottages early to pay for them. Once you have 5 or 6 up, you should plan to have monarchy to get them above the 3-4 pop happy threshold. With the wine online, you can get these cities to 5-6 and above if necessary.
Lastly, dont overfocus on optics; pick up pottery for cottages, currency, calendar once all your city boundaries are popped and probably col and cs as your empire grows.
Bonne chance,
J.