You'll be pleased to know that you don't need any extra accessories... well, except for mega tank cartridges, and I strongly recommend some replacement caps too... but these won't dent your pocket too much at all. The tank carts are pretty much bulletproof so you'll only ever really need to replace caps. Just a simple wash in warm soapy water and the carts are pretty much good as new. As for swapping caps, I used to need to do this pretty much every other refill. Recently I've found I get 4-5 refills before changing caps, and even then I'm doing so more as a precautionary measure.
You've made a wise decision in my book!
Just one last thing to say before you receive them is that with a fully charged battery, it's importanty to take a couple of primer puffs (drawing without activating the battery) from time to time whilst you use them, otherwise you may find you get a slightly burnt tasting vape every once in a while. In exactly the same way, you need to do the same with smokeys, clearo's etc as the higher voltage they put out on a full charge vapourises the eliquid quicker than it does once it's down to 3.7 volts. Believe me, it's a good thing as it means loads of vapour, throat hit etc! But it took a little while for me to find my pattern with it.
All I'm saying is IF every once in a while you get a slightly burnt-flavoured vape, don't dispair - it's easily sorted and a really small issue for the amount of pleasure I'm sure you'll agree they give. Please let me know how you get on, I'll be stoked to hear about it!