hello! glad your enjoying your new hobby! I started the same way, wanting to use this as a stepping stone to quitting but the gadgets took over and im ok with that, lol
Vari volt, unless stepping up to what they call a mod using rechargeable batteries is harmless.
something like the EGO twist or KGO V V (ego/kgo are companies) are simply turning up or down the power coming out of the battery, think of it like a flashlight with 3 bulbs, turn it down you use one bulb less power and less effective, turn it up and more effective,
the devices that vaporize the liquid are just little wire coils in the basic form, giving them a little more power sometimes makes the vaping better. since they come in different power rating with a vari volt device you can fine tune your experience better thats all.
I would start with an EGO twist or KGO/KGOvv battery, they have a standard thread design called 501, there are literally tones of devices made for this threading. get at least two per person,charger etc.
Next you have to decide do I want to stay with cartridges like v2 or move on to a tank like system.
the carts are reliable, easily filled and work for a while if cared for.
after that they have whats called clearomizers which are little tanks with no filling they work better and hold more, but require a little more attention and care. there is also direct dripping which is drip a few drops in the tube take a few puffs then do it again.
then there are big tanks, fill em up, screw them on and have at it for a long time. they work well, hold alot but cant be layed down or they might leak.
hoosierecig.com
smoktek.com
ecigbestsave
3 vendors I use, until more people start carrying a EGO twist kit I would avoid most of the EGO KGO kits cause they include cartridge systems that arent that great. your kind of paying for acc's you will quickly outgrow.
i would suggest a couple battereis and charger then deciding what type of tip you want to try, then check on youtube for more information on that device and how to fill/use it.
then the best part when leaving the world of prefilled carts like V2 sells ---- there are TONS of juice venders selling literally 100's of flavors that blow the V2 stuff away!