Look at it this way...you can invest in the hardware. And try a few liquids until you find what you like. Like Viper Ron posted...3ml sizes or even 5ml. No the nicotine does not affect taste. Flavors are great, even at 0 nic.
as far as hardware...Not sure if you are set on the 510 or not. The 510 has a fairly short use time between charges--couple hours. If you look into the ego, it has a much longer use time between charges.
The ego is a bit fatter...about the size of a standard sharpie. The 900Mah ego battery with atomizer or cartomizer is almost exactly the same size (width and Length) of a sharpie.
Ego come in various Mah---650 - 1100. The lower the Mah, the shorther the battery and the shorther the use time between charges.