I’m starting to like the cows spot. I really want to know what’s in the fog north of the cows. Maybe that would be a better option for a 3rd or 4th city. Lots of green tiles, forests, hills. Closer to AI. Should be a much better spot for building military, and with the wine, the long term commerce yield could be comparable to the gems spot.
+1
If we could REX as much as we wanted, gems would be a good spot. But we can't, of course. Since our city count is limited, every city must provide one or more of the following:
1. Strategic resource
2. Massive production for units (either raw hammers or whips)
3. Settle toward the AI
4. Research (although this is somewhat mitigated since we'll be getting a ton of techs via espionage, right?)
LC himself said that Gems City is a junk. I hadn't really thought much about the city and I was on board until I heard this. I admit that I haven't been actively looking at the save the last week or so but looking more closely, that tundra city is junk. It has lots of forests but after that, growth is slow, production isn't awesome, it's far away from the direction we want to expand, etc.
Pollina brought up the fact that we'll have Monarchy (and HR) about the same time we could get the gems online, so the happiness of the gems is somewhat minimized, especially given the fact that in this scenario, we HAVE to have a ton of MP units in or around Rome anyway.

won't be an issue because we'll likely have a bunch of archers in Rome.
Gems city was a cool idea but it will tie up a lot of our early-game resources (settler, worker + warrior gift, chariots to take the city back, units to keep the city safe while the AI controls it, etc.). We must be able to come up with a better use for all of these hammers.
I would love to take down an AI or two with chariots if possible.
Regarding research, does HBR soon make any sense? Maybe after Alphabet? I'm not sure how long chariots will be viable with the AI being so far away...