How is Deity (Nightmare mode) anyways, just wondering?? Is it really really hard??
Deity/nightmare/large map/snail speed/break pangaeas/start anywhere is quite hard but not yet as hard as vanilla BTS deity. I currently play with SVN 8196 (2 januari 2015).
The new education feature means your tech speed drops to near zero after researching only one tech, from then on you have to progress to Oral Tradition on near zero beakers per turn plus tech diffusion and luck with goody huts. That takes 30-40 turns per tech level. It means you will be really, really behind on tech compared to the AI. Even though I took over my neighbour's capital with a dozen spiked clubmen as soon as I could (pretribemaint allows you to own 2 cities with little upkeep but this is probably fixed in the latest SVN).
When the first AI reached sedentary lifestyle I was 21 techs away from it. When I reached writing, two AIs already could trade money (requiring a tech that was 26 techs away fom me).
Lack of tech also means lack of buildings to build, keeping education in the positive is a continual issue, and upkeep cost for number of cities is extremely high, so expansion is slow. You basically have to develop your economy first for each additional city, even with producing Wealth.
After writing you can buy techs from the AI in exchange for workers (which you should mass-produce for this purpose). Once you can trade money yourself, you can sell those workers for over 600 gold each, and as the AI is swimming in money by that time, it means your money problems are over, too.
I dont specialize my cities as much as I did in vanilla BTS (the rules of C2C don't reward that as much) but I do make a dedicated military city. This city has many good food and hammer-tiles, and I settle all my great generals and cultural heroes in it (unless the hero can build a hero achievement) and all combat bonus buildings, production bonus buildings and military relevant wonders. With my current military city I can build level 8 mounted units. My army consists of 40 level 8+ ballista elephants and a lot of cavalry. Those ballista elephants can in one turn move close to an enemy city, burn down its 375% defense to 50% and still have enough attacks left to soften up the defenders with ranged attack. After that my level 8 cavalry kills the defending units in the same turn. Which means I took the city without my ballista elephants taking any damage. Each conquered city immediately gives a bunch of beakers (usually almost enough for one tech) so the tech difference is shrinking rapidly. I have confidence that I can win this game.