If you go with a M1A1 tank, they are really easy. Go to your local hardware store or plumbing supply and get a small saddle valve. It will punch holes in your carto without much effort. Or you can use a dremel and cut a slot...just be careful not to go too deep. Simply insert the carto into the tank, remove the fill port, fill it up, fill carto from the mouth end like you would any carto (sorry forgot you don't have any stuff yet but it's easy to do), let everything rest so the juice gets into the carto, screw it onto your PV and vape away. When the tank gets low, refill it. The hardest part is making sure that your carto is full of juice BEFORE you start
vaping on it. Once it's full, the tank will feed it.
When using variable voltage, you want to make sure that all cartomizers or atomizers are regular/standard resistance...which is around 3ohm. This way, you can use the different voltages to find the best taste for the juice you're using.
One other thing, make sure you get some atomizers. Atomizers come in hand to test flavors with...then they can be easily cleaned/rinsed out. You also might find that you like atomizers over cartomizers. Plus you aren't ruining cartomizers because you hate the flavor you have.
On top of all this confusion, get a drip tip. I can't remember if one comes with the m1a1 or not. Drip tips feel nice on the lips plus it makes for easy dripping if that's what you decided you like the best. However, there's a little bit of a learning curve when it comes to dripping. Not hard to do but takes awhile to get the swing of it.