How much RAM do you have atm? And if you load a Civ map (not blank) and open up Task Manager, how much RAM does it say you're consuming?
16 GB is more than enough as said above. You won't have any problems with too little RAM with having 16 GB unless you run unoptimized games.
Even 8 GB could be enough for such game in general, though I'm not that experienced with Civ RAM consumption, hence why I ask.