You are exactly where I was one week ago, so I think I can help.
First, listen to what JenJen says. She's one smart lady who won't steer you wrong.
Last Sunday, I ordered the cheapest starter kit V4L has, the mini kit, just to check it out.
Vapor4Life- Electronic Cigarette: Vapor King Mini Kit with USB Passthrough
It arrived on Wednesday. I spent most of the evening checking it out. I vaped through one cartomizer as fast as I could (almost) and took it apart to see how the refilling part would go. It turned out to be very easy and far less messy that refilling 3-piece carts.
I'll cut to the chase first. Before I went to bed Wednesday night, I ordered the Ultimate Ultimatum kit. I was that impressed.
Vapor4Life:: Because it's your life :: Electronic Cigarettes & Alternatives to Analog Smoking :: Vape-On Baby!
I went with the auto batteries, but they have the same kit with manuals too.
If you only use pre-filled cartomizers, the cost will be significantly higher than refilling your 510.
Refilling the VK is so easy it's not funny. All you need to buy is juice. One or two simple tools you can make or find lying around the house and you're in business.
Since each cartomizer comes with silicone caps (similar to the 510 carts but a much better seal) and a little plug, you can carry extra cartomizers almost any way you want, including in your pocket. No leaking!
Want to load a cartomizer with a different flavor than it came with? To do this you need some fairly sophisticated equipment... a pair of pliers and a kitchen sink.

The pliers are to hold the cart (gently!) while you rinse it out with hot water. Blow through it and refill.
I hope this helps. If you want more info, there is tons of it and great people in this forum. All you need to do is ask!
Oh yea, WELCOME!
Bob