There's 3 methods. 1) atty+cart, 2)Direct dripping (no filler in cart) and 3) cartomizer. (there are other exotic dripping devices, but I won't go into those). For 1 and 2, a drop of e-liquid will give you about 4 long puffs. You can get a max of 3 drops in method 1 before the atty starts to flood,
so that's about 12 long puffs.
I just got my new Joye 510 manual with atty today. When I filled the cartridge I was able to get about 12 drops in without it overflowing. Not sure what you use that only lets you get 2-3 drops in it (unless you are strictly dripping) but am curious to know so as to help others. Thanks