Don't quote me on any of this, I'm still learning! (Heads are the same as protank 1/2/mini, so there's still quite a few articles I haven't read yet, I'm sure).
For a basic coil above 2 ohms, wrapped around 2mm silica, 4 to 6 turns of 32 gauge (0.2mm) seems easiest.
Similar construction, under 1.6 ohms, 30 gauge (0.25mm), works out at about 0.2 ohms per wrap (2mm diameter coil) plus a bit for the legs.
I'd like to know the best way to do a simple build for 1.8 to 2.0 ohms! 31 gauge? I've yet to
buy myself some of that.