If you have 2 batteries then I wouldn't worry about getting more. All the 'systems' they talk about are really just a battery and a switch (don't tell them and burst their bubble). If you need more batteries or back ups, buy batteries, not a kit. You do not need a kit if you already have the charger and especially if you know what you like to use as a clearomizer or carto. I think I got the most for my money with a 1100mah pass-through battery (kGo knock-off) that charges with a USB cable (like a cell phone) and I can still use it while it charges.
A low resistance (LR) Star Dust or Vision eGo is a good investment at around $5 each. Not perfect, but better than most of the others.
Now with the batteries... Does it matter if I get an actual joyetech battery? I have two, but my husband is using one. So we really are only using one each. Which has not been a problem, we have been charging religiously at night. I bought a second charger, thinking it could plug it in to my comp no problem, however it doesn't have the wall adapter and it only charges when my comp is awake and I am using it.... I do have a USB/wall adapter for my phone, I was wondering if i could plug my e cig charger into it and charge my e cig, I'm worried I'll burn it out or something though?