+7 on the Kayfun I think. Get an Ohm's Law calculator. Lots out there for computer or android, etc. volts or watts, doesn't matter as long as you can make the conversions. I use this calculator a lot:
Watts - volts - amps - ohms conversion calculator
And several others on my phone. The MVP V2 has an ohm meter and uses VV or VW, might consider an upgrade. Most all other APV's have a built in Ohm meter now. They are that important, and critical for building coils. Lots of great videos out there, but one name comes to mind for coil building:
Rip Trippers
He does several YouTube videos on the Kayfun. Here's an advanced double nano coil. However, use a larger drill bit (5/64") and build one micro coil, not two nano coils, and you can use everything else in this video:
Micro coils with cotton is the cat's meow for me on the Kayfun. Rip Trippers shows you how to build micro coils and wick them with cotton on numerous videos. They are really easy after half a dozen attempts (or less), and vape like there's no tomorrow. My ADV is a kayfun 3.1 on the Semy in hybrid mode. Surprised I got to this point, after clearos for 6 months, then carto tanks for 6 months. Now the RBA's are just a magnitude better vape, and I may never go back to other devices. If I do use carto tanks, I'll probably get a Sophia for use in my nice carto tanks. Nothing like building your own coils.
You will need some build gear. This is a good video for what you need:
https://www.youtube.com/watch?v=Rq6Iat2SmIA
Also, study battery safety at Battery University. Ohm's Law videos are helpful:
https://www.youtube.com/watch?v=xc90pdATEM0
Good luck in your VapeQuest. Power up and Vape On!
Edit:
BTW, this Grimm Green video is good for both Ohm's Law and the Kayfun:
https://www.youtube.com/watch?v=WyBIikc9wnY&list=PLaKl-QCA0q_qTNN9ikf9yYFcLK2jSdMve