I've only been building for about 4 months now, but in my experience an ohm reader is a must have in your arsenal of tools. This way you can build different
coils and safely test them before putting them on your mod. The IPV2 is a regulated device, so in theory you should be fine no matter how you build your
coils as far as safety goes, however I still like to use it to get a more precise reading of your ohms. They're usually about $15-$20.
You'll probably find that you'll end up using different diameter coils on different atomizers, so there is no perfect size drill bit per say. It seems like a lot of people tend to favor a 5/64 drill bit for general purpose though. I personally have been using a small screwdriver that is just under 1/8 for my drippers with 26ga kenthal wire. 28ga will definitely give you higher resistance per length. For a dripper, I usually sub ohm, and hover between .4-.6, which is generally considered a pretty safe level. Since you are a beginner, do NOT go under .3 ohms. Remember that more wraps and smaller wire increases resistance and vice versa.
Hopefully that helps some, and others, feel free to chime in as I am still somewhat of a rookie too.