On my STMs I use 30ga twisted-pair on a 3mm tool. IIRC, I use about 6 wraps. The finished coil comes out to .7-.9 ohms and has a very good balance between vapor production and flavor. ...for a STM anyway.
Yeah... I have been using these for about the last 10 Days...
$3.24 Authentic MKWS Nichrome Resistance Pre-Coiled Wire for RBA Atomizer (15-Pack) - 30*2 AWG / 0.25mm*2 dia. / 1.2ohm at FastTech - Worldwide Free Shipping
They seem to be a Tad Better for both Flavor and for Vapor than a Single Wire.