1. Worker stealing is very powerful. It needs to be evaluated, whether stealing Workers has the greater benefit (common situation) or whether the diplomatic relations towards a certain civ are more important. A tech-partner can be very valuable, having a stronger empire onesself however is too. Someone wrote "Worker stealing changes the game" . I've gone over to trying to steal Workers but only if I'm sure that I can steal safe and that the diplomatic relations aren't ones that I want or need.
2. GM-137 was on Marathon and in HoF it's a lot about getting the greatest benefit at the lowest cost. Mathematically building a Warrior and stealing a Worker makes perfect sense. Worker first is the peaceful approach that gets advised in S&T, it's a safe approach on how to win civ. When playing competetively it's about winning faster than an opponent, if playing multiple maps is no problem, then Warrior -> steal Worker is better, if winning a certain map safe at all cost is required, then building a Worker onesself is the right approach because it comes with no risk.
3. Expansion through war is simply more powerful in civ, because units and Settlers aren't perfectly balanced. Peaceful expansion is a lot stronger than many think, but cities can be conquered for way lower costs than they can be self-built.
4. Best tech to oracle I know is Civil Service, but depending on the difficulty level and the map Currency sometimes even can be better and it's a lot simpler to oracle Currency than Civil Service. Metal Casting is the best choice when wanting to trade a lot. Oracling CoL is a very good approach that doesn't shine well under the light that Oracling Currency is possible, but it's the easiest approach when Oracle makes sense at all. Oracle Construction imo. is weak, empire's are not ready for an Elepult rush so early so oracling Currency and then self-teching Construction with the
one can trade for is better.
Techs a player should research imo. are Currency, CoL, Civil Service, Paper, Education so basically a straight beeline of economical techs that leads to Liberalism or further. Techs the AIs like to research are basically all others so Monarchy, Calendar, Construction (hard to trade for because unlocking many things, which is why self-teching sometimes makes sense) , the AIs go for Aesthetics late usually, Metal Casting seems pure chance to me, sometimes the AIs research it early but most often they research Calendar, Construction and Monarchy first, AIs like Feudalism, Machinery, Engineering, Philosophy is similar to CoL, the AIs love it when they can be first but trading for it is not easy so self-teching might be required, past that point I didn't record what the AIs like to research because I usually win the game then.
The last is very harshly dependant on difficulty, the lower the difficulty the more techs a player needs to self-tech, this completely changes the rules. If self-teching i. e. very important, then i. e. teching Banking early is very powerful because Mercantilism with REP is a huge economical boost.
5. I wrote a guide on the economy, you find it in my signature.
Wanting to keep the research slider at 100% is a common mistake of players in the beginning imo. . A larger empire also generates a larger base sum and a lower-slider with a higher base-sum can still lead towards the same sum while having more production and a higher research potential. It's right, smaller empire initially research faster but the gain in production by having a larger empire is more important. Cities easily can sustain themselves at 0% through TRs, so then the only real cost of a city is the rise in maintenance through number of cities. Cost through number of cities is capped though so there comes a point at which each city doesn't generate an additional drain because of raising the maintenance of all other cities aswell. Cities then even boost the economy of an empire while giving extra
and
and that at size 1 already.