BenitoChavez
Elderly Tortoise
Cultural > Maritime > Mercantile > Militaristic > Religious
This.
Cultural CSs are the best way to get extra social policies especially early game where all you have for culture are monuments, amphitheaters, etc. Martime is always good for more citizens. Mercantile is either the top or bottom priority depending on my current happiness levels, so the average is right in the middle. Militaristic can be useful but are hardly game changing. Religious is most useful very early in the game for a pantheon/religion but aren't necessary otherwise.