Thanks for your report and the encouragement! I only have three achievements left, would be great to knock this one off. Any particular pointers regarding settling that might be useful, given that I've put no thought into that yet?
Three left. Oh, that is so awesome! It makes me want to focus more on mine, especially if we get those extra ten in the next patch or whatever it is.
The settling issue is something you get going from your very first turn as others have pointed out here. Also, like it has been said, all new cities will produce settlers until it is no longer useful because of time/turn constraints. All conquered cities always build an Encampment first. Also, you must have 205 points to win, not only 200. This means you need to produce/buy 11 settlers yourself. The one you get at the start doesn't count, although this one is crucial for getting you going.
Location and money are absolutely key. First, location: my suggestion is, of course, to settle the settler given at the start left of the wine to the east immediately on turn one: Again. Both Pella and Agai will need to maximize their production for settlers until it is not feasible anymore because of time/turns left. The first settler Agai produces needs to settle next to the closest mountains, east of Gordian, two tiles south of the water (by the river) because it is has a lot of production in the form of woods and, if your are lucky to steal workers, they can chop these to expedite your settler production. The next location where it is best to settle is north of Arbela, on the road, next to the oranges. In my very first try around when the scenario first came out, once I settled it opened up the woods close by and of course the hills and the copper close by. This time around it did not open the tile of woods, which sucked, but I managed to win on Deity anyways. They tweeted the scenario in one of the updates. Also, I won despite the issue I mentioned in my previous post that when any city finished building a settler all other cities producing settlers would increase or maintain their turns left of the previous turn. This time, this meant that the city north of Arbela, didn't give me the settler on time. Regardless, I made it and so can you, but having money helped so much.
So, second, money is critical. I got 3 or 4 Hetaroi out of Pella, 1 out of Tarsus and Parsa each, and bought only 2 or 3. This was key for me so that on turn 34 and 35 I was able to buy settlers which cost a lot and go up in cost by 60 gold each time you buy one. So, it was great to grab all the extra units you get by having Alexander next to Athens (Hoplites, of course essential for fighting in Patala against the Varu), Halicarnassus (the Galley to destroy the galleys around and possibly help out taking Tyre along with the Quadrireme you need to build second in Athens), Babylon (archer very helpful going north of Babylon), Parsa (the Immortals are key for fighting in Pala) and Patala (the Varu to expedite getting Taxila north of Patala). This way, you don't spend money on Hetaroi or other units. This reminds me that I did get two workers, I believe, out of Sparda to help Agai and other new settlements. Also, micromanage your cities. Make sure the correct tiles are being worked to maximize production when you need to and gold also. Sometimes you need to fiddle with this because the changes you make inside the city tile assignments don't go into effect unless you click and click again things around. Issues with the scenario, I guess. Also, to maximize your money, from the very first turn until you buy your last settler, unless you are producing units, force gold production in each city nullifying production and food, unless the city shows you in red that they are about to lose population. You don't want any conquered city to lose population because it could mean losing gold/turn and each gold you get is critical. Also, whenever you get the chance to pillage a tile that produces gold, do it, unless it will affect production in and you need that for a few turns. I got a lot of money from Tusa on up north. Of course, pillaging strategically for health also is very helpful.
Finally, one more point on location, the rest of the cities need to be settled close to conquered cities where you can buy the settler and move them in one or two turns. For example, one of my last cities was founded south of Thebes. If you get many +5 movement Generals, you can place one next to Thebes and, when you buy the settler there, it will help move it quickly south and settle in one turn. You can do that in other places too, but it depends how your game is going. Just inspect the map with the Settler lens and figure out which locations are best for you considering your particular game. Also, make sure you try to illuminate as many enemies on the way, not only for the 5 points to get more generals, but so that when you are settling your cities towards the end, they are not lurking around and preventing you from moving lonely settlers around. I think this enemy units were programmed to appear in key locations right as you are about to do something important.
Best of luck and enjoy! It is my favorite scenario now.