I might have to try this also
It's absolutely a great way to improve your game skills. You learn new things if for no other reason than having a much different starting point than you would find yourself in. And you have other players' examples to compare to.
how do you guys broker techs? Start with less advanced civs and work up to the most advanced?
I can't find a strategy guide, but I'm sure they're out there. They typically focus on "zero research", min research or strategically-chosen research from the very beginning. But the principles work here.
(TL;DR: You have to find a civ close enough to you in advancements that needs a tech you might be able to acquire, over and over again. Try to get at least two techs for every tech you acquire. Focus on required techs, especially those which are prerequisites to two others. Look at leader head pics and wonder builds in progress to gauge how far ahead the others are.)
In assessing the situation you look at wonder builds in progress to get an idea of how far ahead your opponents are. (And of course which age each civ is in which is evident by their leaderhead photo or game assistant.) In this case, Germany is building the only Industrial Age wonder, and it's two techs into the IA.
AI are pretty wonder-happy, so it's reasonable to assume Germany may be the only one quite that far. That's a minimum of two techs into the IA, but Germany is a scientific civ and therefore got a free tech once they got into the IA, so there's an okay chance most of the IA civs are just barely into the IA. However it may also be that they have even more techs that don't enable wonders.
Coal and rubber are IA resources that can indicate where they are on the tech tree in IA, too. If you wanted, you could spend for embassies and/or investigate capitals and see their trade resources (and units defending). But I didn't think I needed to, and I wanted all my money for catching up in tech.
But I did see China I think had some rails built, so I know they're at least that far and have coal.
Anyway, there are three techs in the MA still which are the ones I'd have a shot at finding a tech they don't have, and Arabia in fact lacks Chemistry but has Theology, and I have neither. So that's where to start pulling the thread: acquire Chemistry, use it to get Theology from Arabia, then see if there is another thread to pull.
Before I did that, though, I noted Egypt was working on Smith's, so they clearly had Economics, but neither Arabs nor Mongols had any wonders in progress, so they presumably weren't as far along, so there was hope to find more threads to pull.
The human play can do something an AI would *never* do: trade away their last of a resource. I could also buy tech relatively cheaply, but that just gives the AI which is already ahead the ability to crank up their research faster, and they can all trade with each other so that's not a great way to catch up. Note that zerksees bought even the last Modern Age techs, so he never actually "caught up" in research. I'm actually hoping to be at parity with the leaders by mid or late IA if it's not already too late.
Anyway, Russia had no horses, England had no Saltpeter, and Arabia lacked all three resources. I intended to keep my iron to stockpile Samurai, but I wouldn't have started with Arabia anyway. I want to get Chemistry then use that to get Theology, a "two fer"...effectively getting two techs for one resource.
...oops...or that was the original plan, but as I read my notes, I actually got Theology from Russia first . Did I goof? That would have sucked if Arabs didn't have Education and beyond. And then I got Chemistry and Education from England with the Saltpeter. Again, would have sucked if Arabs weren't past that.
But they were, so I got both Banking and Astronomy from them for Chemistry, paying out the most money, but those two techs opened up access to a bunch of others, and Arabia was clearly a bottom feeder civ like me.
So I'm not sure if I had a good indicator the Arabs were that far up the tree or if I goofed up and lucked out.
Anyway, at that point I saw that none of my MA peers had Physics, and both Arabs and Egypt lacked Metallurgy. (Well of course Arabs did as Chemistry is a prereq for it.) I'm mostly ignoring the optional techs at this point as I want Military Tradition for cavs, and I want to get the mandatory techs to get into the IA.
I planned to self-research Metallurgy a few turns and hope to trade it to Egypt or Arabia, and maybe they'd have Physics by then.
But Arabs turned up with Metallurgy the very next turn. (Probably with the money I was giving them...damn!) I just realized they had to have traded for it as they lacked the prereq until I traded it to them the previous turn.
So Egypt was my only trade partner left for Metallurgy, and I didn't want to wait because they might acquire it before I do, so I used my Iron to get Metallurgy from Arabia, and I threw in the world map and a bunch of optional techs (untradeable since everyone has them) because he had nothing else to offer in that trade.
That put me on the path to being able to self-research Military Tradition which was my primary target since once the original deals end I'll have my horses and saltpeter back to build cavs.
I don't think there is a better offensive unit between cavalry and tanks, so it's YOLO war time. Coercing the world into war slows down research, and catching up quickly isn't as critical, and it's not impossible I'd be able to demand a tech for peace if I survive long enough.
So I'll still definitely be looking for tech-for-tech trade opportunities, and if I conquer more resources I'll trade away any extra or unneeded, but I don't expect to trade away my only iron, salt, or horse resources anymore as I have to keep making military.
On the other hand, I really need to get into the IA, so I might do something crazy if it looks like I may lose my chance to barter my way into the IA like I almost did when Egypt was the only civ (besides me) without Metallurgy.
Edit: In retrospect, the last two trades were probably bad deals. I didn't get two good techs for one. I got Metallurgy a few turns early and a bunch of optional techs that don't really help, and then I gave England Metallurgy for Economics, a mostly useless tech. If I had waited and watched, I might have still been able to get Metallurgy but also Physics. Otherwise I would have had Mil Trad 6-8 turns later than I did and maybe still have iron. But I did get a world map, and that was sorely needed.
Edit 2: Yeah, I'm pretty sure I goofed up big-time by trading for Theology first. I just lucked out. It should have been acquiring Chemistry first and then trading it to Arabia for Theology and probably WM. But maybe it worked out for the better since Chemistry is worth so much more than Theology.