I always recommend that if you never built a coil and you are venturing into doing so, learn how to wrap and build 1.2ohm and higher coils on a vv/vw mod before venturing into mechs. Learn your basics first and use nothing less then recommend IMR batteris for vv/vw or mech mods. These are Sony VTC4, VTC5, purple eFest, or AW batteries.
Youtube is a great place on where to see instructions on wrapping different coils. It's the place a lot of people have learned and then taken what they like and mastered it for their own purpose and liking. No two vapors will like the same setup and coils when it comes to those that use mech and build coils.
Cheap RBA that is good? That's an oxymoron. You will never see me recommend anything below an Ehpro or Hcigar for a Kayfun clone. It's my personal experience. If you want cheap and like headaches and rebuilding more then you vape, then by all means play Fasttech Roulette with one of their Kayfun clones.
There are other good clones out there other then the Kayfun as well. If you want Genesis style, you have the RSST, AC9, Kraken, etc... Top build with steel mesh still holds a place in my heart.
You also have the Russian 91% clones by good manufacturers.
In many ways it will come down to your taste and preference... just be safe with whatever you choice and don't regret your purchase.