Once you try a high quality cartomizer and find that you like it, consider investing another $20 for a pyrex cartotank from
IBTanked - Get Tanked With Us!. I did a review of them here:
http://www.e-cigarette-forum.com/forum/tank-reviews/349222-ibtanked-pyrex-glass-tanks.html.
A tank is just a device that keeps the cartomizer's polyfill bathed in e-liquid for all day use. No need to frequently top off the carto with more liquid when it runs low, the tank acts like a built-in juice bottle. The tanks that utilize a pyrex glass tube seem to be the way to go now because they are immune to the effects of some liquid flavors that can crack/melt the plastic tubes previously used, and being a totally inert material the glass does not cause a "plastic taste" that some people could detect.
Tanks can be of two lengths. Standard (uses a 35mm long carto) and extra long (uses a 45mm long carto; DCT tanks). Just be sure that either you match the tank length to the carto length, or match the carto length to the tank length.
I recommend new tank users to buy cartos with holes already in them, preferably laser-drilled. Self-punched cartos, or carto's that have been punched by the vendor, can be out-of-round (distorted) to the point that they are difficult to pass thru the tank. Laser-drilled cartos eliminate this problem, and also eliminate any user error issues related to punched cartos that can frustrate new tank users.
Two vendors that I highly recommend for laser drilled cartos are Ikenvape and Smoktek. The Smoktek site allows choices of dual or single coil, 1-2-3 holes, and ohm choices (Smoktek cartos are only for the extra long or DCT tanks). Ikenvape offers both standard or long (mega) lengths, single coil only, and only 2 hole design. Both are highly recommended:
Ikenvape cartos:
https://www.ikenvape.com/SearchResults.asp?Cat=1860
Smoktek cartos:
510 Tank Cartomizers
The following video goes over basics like
how to fill a cartomizer and
how to fill/assemble a cartotank: