Get a smokteck DCT
That is hardcore personal opinion.
What he said ^^
Maybe if madvapes didn't drop their stupid watermark on everything I'd try it^^
Overall, I'd say get a DCT with a drilled hole and a plug, you fill from the side, and once you get it down, you'll NEVER have a problem with spillage or leakage. Get the fat drip tips, and your tank wont slide off (though I've never had that happen anyway).
I ONLY use the Smoktech 2.5ml DCT as of right now. I'm working on modding my carto's now, to see what kind of interesting results I get. Anyway, don't listen to the people who are trying to scare you into or out of anything. In my opinion, grab a few different things, and if they require components a few refills for each. Figure out what you like, then stick with it. Worst comes to worst, get verified on the forum, and sell or trade the stuff you're not interested in on the classifieds... (I am personally planning on buying a few different types of tanks, as well as 4-5 6ml smoktech DCT's and a 2-3 more smoktech 2.5ml dcts ( I currently have 2)
PS. My experience with the Vivi nova is: it's complicated, and it produces a nasty burnt taste most of the time!