Wendy, that's a good kit but I would definitely pay the extra $6.00 for the 1100mah batteries instead of the standard 650mah batteries. That's only $3 per battery for the extra run time you will get with the 1100mah batteries. I have the 1100mah KGO and one of them lasts all day.
An atomizer is basically just a cartomizer without any filler/stuffing in it. It's short and you can look into it and see the coil in it. You drip 2-3 drops of juice into it and then vape until you start getting a burnt taste (usually 4-6 pulls). Then you can pick another juice and drip 2-3 drops of that into it and vape. That way, you can test different juices with one atomizer. If you mix juices in a cartomizer without thoroughly cleaning the cartomizer (by boiling them several times), you get mixed up flavors (because you never completely get one flavor out of the filler material). So, to test 8 different juices with cartomizers, you would need 8 different cartomizers.
You don't HAVE to have an atomizer, but you will WANT one while you're testing juices and trying to find your favorite juice.
I'd also recommend buying a few drip tips if you're going to get an atomizer or any cartomizers. Just like with the atomizer, you don't HAVE to have a drip tip, but you will WANT one (or several).
For atomizers, cartomizers or clearomizers (or any other thing that ends in "izer"

), get the low resistance (LR) ones. Such as 1.7ohm or 2.0ohm. I think the clearomizers may only go as low as 2.4ohms (not sure), but get the lowest resistance ones. DO NOT GET dual coil anything. Single coil only.