It depends of some important things : -Rush a neighbor or not -Enough traders -quality of land -your personnal goal -diff. level It also depends of player's xp and skills. There is no magic formulas. But generally, a 2 cities NC(then 2 more right after) is probably the ''safiest'' and 'easiest'' way to get education and open rationalism at a good rate. Main reason is that you can normally find a very good spot for a 2nd city with lot of luxs and ressources to sell while keeping a good amount of happiness. This allows you to sell a lot of stuff, rush buy important buildings and work on a wonder or 2, wonders that can help your science going up a bit faster from a long term view(Pyramids, HG, etc). But in term of production and power, nothing beat a 3 or 4 cities pre-NC approach. If you start with 4 cities pre-NC and want to get huge and fast science finishes you should take a lot more cities from the AI and most likely very early(starting with CBs in most cases), annex them and rush buy science buildings in them. This appoach is easier to achieve at emperor or below. For immortal or deity, a 2 or 3 cities pre NC approach works best. You can stay small and sign a lot of RAs. At these levels, RAs are a lot more valuable.