Personally I use the Smokeless Image Volt and their X2, mostly because I think its a great product and their prices are very reasonable. I have never ordered from V2, however I know they are a reputable company. The only thing that I have heard about them is that their prices are a little high and that sometimes they take a little longer to ship than others. I am sure your CC will be safe though.
As far as refilling your cartomizers, there are generally 3 ways, dripping drops into the top with the rubber stopper off, a condom fill method or with a syringe. Most people do the first 2.
For a condom fill, when you get your cartomizers you will see they have rubber caps on the ends (the condoms). Take them off, fill one about halfway and then slowly put the cartomizer back in, either end will work. Some people put in the connection side, but I prefer to remove the stopper where you mouth goes and put that end in. That is mostly so that I dont have to clean off the connection side. Then just let it sit for about 20-30 minutes, blow through it to make sure the air hole is clear, and you are good to go.. Make sure that you clean off any juice on the connection side of the cartomizer.
For juice, there are several companies. I would definitely recommend that you buy some blank cartomizers and order juice from other companies. On average you should pay between $10-$15 per 30 ml bottle. One company you can look at is vapedudes.com. I have never had a juice from them I didnt like. They also have a couple of great promos for new customers. the first one is if you enter the code "fbfree", you will get a free bottle of juice, no purchase necessary. They limit the number of these they give out each day, so try early, if it says there are no more for the day, try the next day. The other code is "vapedudes" This will give you 40% off your order. Both of these can only be used one time for each customer. They will however, allow you to use both codes on one order. On my first order, I got my free bottle, plus 5 other bottles for $12 including shipping. Also, I recommend that you buy smaller bottles of juice (5ml to 10ml) until you find what you like. Many of us have made the mistake of ordering 30 ml bottles of a juice we never tried, only to find out we hate it. Juice is completely a personal taste thing. Something that I may love, you may think is horrible.