I always just used watts to keep it simple.
Eventually, you will want to save some money and use the mini rba to build your own coils. Which is why I purchased the toptank mini atomizer back when i was starting out. I pretty much only use 3 types of wire. Kanthal (cheap, easy to get, easy to use), NiChrome (slightly better flavor than kanthal) and stainless steel (best flavor, a little more expensive, lower resistance *so a little harder to calculate your build with*)
I use SS now either for low ohm builds or for wrapping coils to make Claptons. (but don't worry about that until later on)
Main thing is stick with it. If you really feel like you are dying for a cigarette.. turn your air flow and wattage down a bit, and sit down for a 5 minute puff session until the urge passes. It helps and it works. Kind of replaces that "ritual" smoking, like with coffee, after meals, before bed.. on breaks. etc