It really all depends on your own personal preference.
I started out with a eGo-C Twist and used a 510 DCTank Cartomizer/DCT tank 3.5ml and 6ml. I guess depending on the juice that you are using will give you variations of vapor production. you can also try an Innokin iClear 30 tank which from my experience, also gives a good vapor production, although you do have to give it some effort to inhale the vapor lol. But my favorite now are rebuildable atomizers which gives me clouds, depending on your build of course! But that my friend you have to do more research before trying it in on your own (just for safety and preventing from messing up your ecig as well).