Having just been through this, I can offer some advice from someone who was in the same position not too long ago.
First, you're going to have outlay that you don't expect. You need a TAB or TAB-like device to measure ohms and fire. You'll need tools like scissors, tweezers, wire cutters, pliers, precision screwdrivers, and a jig (not really necessary, but makes it easier to find your desired coil inner diameter very easily.
Bookmark this page:
http://www.steam-engine.org/coil.asp and save yourself a load of calculation and/or guesswork.
Last, if you're not inclined to working in micro-miniature, I would purchase an inexpensive RDA (clone is fine) with a Velocity style deck to work and practice on, something 17mm+. The deck on the Kanger RBA iirc is something like 10-12mm.
Adding in wire and cotton, I would plan on an initial outlay of around $100 unless you can find a PIF or used items.
The Kanger SSOCC heads are around $3/each. If you're not using super-sweet or "dirty" juices, a single Ni200 coil should last you most of a month at 10ml/day. I can put 250ml of many juices through one before it really starts to suffer. So, while more economical in the long run, or when building multiple devices, if you're just working with one or two atomizers, it will take quite some time to recoup your outlay.