Single coil or dual coils? Are you going to use it on a regulated mod, hybrid mod, or unprotected mod? What battery/batteries are you going to use? What are you going to use for wicking? What nicotine level are you planning to vape and on what (RTA or RDA)?
Higher gauge number equals more resistance per unit length. Larger inside diameter coil wraps equals more wire used per wrap equals less wraps to obtain resistance. You also can download the Applications Vaper's Toolbox and Steam Engine.
Edited to add more questions.