Teched agriculture, BW for chopping, then wheel -> pottery for cheap granaries.
[...]
Around 700BC - 300BC my economy got fixed as I built the GLH, the pyramids in the old Incan capital (& switched to representation), and finally libraries came through.
Without cottages/luxury resources to raise the happy cap, Pottery = production.
Peter being expansive is a bit of a trap in a snack economy game :the real tech you want before maintenance rises too high is Writing. And that may require some care on this map : commerce sources are few.
The specialists have a very high value early on compared to say... a river tile. Writing also enables Open borders, which essentially is free commerce - as long as you have a road to your rival or a connexion via Sailing.
Put otherwise : without early gold/gems/silver/fur and without early cottages, settling + building units + researching Pottery AND Animal Husbandry before Writing is too greedy (I'm assuming AH went first).
On this particular map, I would say Pottery can be delayed quite a bit. AH is another story because it gives you some of the best tiles you could work;
Sidenote : you also delayed Fishing for a long time, which has hurt your commerce. 4 commerce from 2 fishing boats is a lot, early on. But I guess it's either the workboats or the rush. So... ok
The road to Writing is also about maximizing commerce but not rush-related.
From my last SE econ game I found it tough to decide when to shift from slavery to caste - both of which work well with food excesses. Any advice?
That's a very broad question and the right advices would depend on context.
1- The Spiritual trait or a golden age allow for very early uses of Caste System. I'm not familiar with that, though. Let's... just... say... those add flexibility. If you're not in one of those case, the short answer would be : not too early. I guess.
2- Slavery is straight production : it provides you with expansion capabilities (workers/settlers/military) and infrastructure.
So if your empire can/should get larger AND if your empire still needs a lot of infrastructure, Slavery will net the best result.
Expansion and Infrastructure can go a long way into the ADs. What amount of infra do you need ? When do/will you have the opportunity to grow your cities ? When does straight production become superior to Slavery ? Those are the issues.
"People" speak about a size 10 city as the threshold.
Other than that, Universities are often whipped to accelerate the building of Oxford. Afterwards, you should have the infra you want. Possibly much earlier, I assume.
Military, one can whip throughout the game.
3- Both civics work great with food surplus, right. However, they do not have the same requirements :
To support 3 scientists in a city, you're likely to work 2 tiles, which mean a happy cap at 5 minimum. Say you want 6 scientists, the needed happy cap will be 9 or 10. How many scientists you want to run partly depends on how long it will take to produce a great person. Early on, 2 or 3 may do, especially if several cities run 2-3 each. Later on, you will need much more if you want to keep popping GPs.
Now, on the requirements, consider the following :
We assume a city that would hire scientists. For the sake of multiplying science, that city has built a Library.
- What is the cost of running Slavery ? We can't run more than 2 scientists. (if we get a temple/market/courthouse, we may still run more specialists...)
- What is the cost of running Caste System ? We can't hurry production anymore.
So that's a difference in quality, much more so than quantity : infrastructure may offer the same effect as Caste System but Slavery's effect is not replaceable.
We could ask : how many scientists should a city work to make up for the loss of Slavery ? Is 3 enough ? Would it be 4 ? Or more ? How many cities would that concern accross the empire ? What about the cities that do not run specialists, do they still need Slavery ? (-> back to the issue about infrastructure first)
In the end, the time needed to produce a GP and the production you need vs the tiles you work will factor in. Also : do you need a particular GP or specifically a scientist or a merchant ? In the early game, unless you plan a bulb, a GP or another often won't make a big difference...
Disclaimer : I've used the term "need" very often. I'm not talking about absolute needs. Relative is the thing.
Hence... gotta try alternatives out
I hope that helps.
Also I couldn't play it with the BUG mod either 
with 21 cuirassiers in 2 stacks (and more on the way):
(Kossin would be proud 
). By 1500AD HC had been 
Do you really need to go past size 8 at 500 BC ? It may be better, but building settlers/workers is a classic way to halt growth.
