Personally, on huge maps (Small Continents Plus with LOW seas, giving it a close-to-pangea-but-with-coastal-start-for-everyone feel) I run 18 civs and 27 CSs. Theres enough space to expand, but there'll still be border-rubbing neighbors enabling a decent amount of warring.
I always go for every 1 civ, 1.5 CS.
I always go for every 1 civ, 1.5 CS.