bubbe11, have you tried ecigs at all? Do you have a favorite between the 801, 901 and 510?
The nice thing about the Prodigy is the versatility. If you buy one kit such as the 801 and find you prefer something else, you can get a different adapter without buying a whole new rig. All you would need is the adapter and different atomizers.
Which kit to start with is a very personal decision. If you're just starting out, I would suggest the 801 as they seem to be the most forgiving for new vapers. You can always try other adapters later once you get the hang of the whole process.
The kit comes with everything you need to get started except the liquid which Steve sells also. It comes with 2 sets of batteries but if you'll be away from a charger for long periods of time you may want to order another set.
You defiantely need a spare atomizer or two. If you're sure which type you want go hog wild and order a bunch. Steve gives bulk discounts. Go to the atomizer of choice and click on "view quantity discount". If you're not sure whether you'll be happy with your choice just order a couple of spares to start.
You said you'd probably drip so no need for carts. Steve doesn't sell them, he recommends dripping.
So basically, you need a...
*Prodigy kit (either 801,901 or 510)
*E-liquid in a flavor that sounds good
*Spare atomizers that fit whichever kit you bought
*Maybe spare batteries (you can always get more later)
As far as the pass-through thingy

, it is also 5V like the Prodigy but requires an external 5V power supply. You'll need a wall plug USB, a Kensington Power Pack, external powered USB hub or something similar as it's not technically recommended to use the USB port on your computer, even though it is done by some. It is a cheaper alternative to trying 5V. Like the Prodigy it has different adapters for different atomizers. But these adapters aren't compatible with the Prodigy.
If you decide to go with the pass-through you'll need...
*Pass-through (801,901 or 510)
*Eliquid
*Spare atomizers
If you have any more questions, just ask. Somebody will jump in with an answer.