First thing, as a new builder you shouldnt be using stainless steel. For several reasons:
1 it is more expensive - so waste costs more
2 resistance is much lower than kanthal or Nichrome. So you have to use a lot more wraps.
3 it takes more time to heat under current load. SS is good for clapton wraps since it conducts heat quite well, but not so great as a core wire (unless you use 28ga or higher)
4 SS oxidizes faster than NiCr or Kanthal so you have to replace them more often
5 SS requires heavier coils (more wraps) so take more power to heat meaning shorter charge time on your batteries and thereby also shorter battery life as you have to recharge more often.
ALWAYS use top quality, first run, brandname high discharge batteries. Samsung, Sony, LG. House brands like surefire are rewrapped factory 2nds that have FAILED manufacturer Quality tests, but still ok for flashlights. Is it worth maybe blowing up a $100 mod to save $2 on batteries (or worse if you use a mechanical (see youtube videos re exploding mods)
Remember, with dual coils you divide resistance by 2. IE.. 0.5 ohm + 0.5 ohm = 0.25 ohm total.
So 24ga SS dual coil on a 3.0mm id core requires 10 wraps per coil and between 100 and 160w to power. (according to how warm you like your vape)
See:
http://www.steam-engine.org/coil.html?mat=ss316l&s=dp&r=0.25&hf=360&awg=24&id=3
I would suggest 24 to 26ga kanthal or nichrome to start and some 32ga SS wire to wrap claptons, when you feel comfortable. 32ga is easier to handle.
I also HIGHLY suggest that you check that your atomizer has PEEK insulators not rubber. Rubber breaks down quickly with heat, PEED doesn't. A damaged insulator can cause shorts. Regulated mods will not fire.. Mechanical mods go directly into hard short, battery thermal run, venting and can explode. Its better to spend a few extra $$ on either authentic or a clone with PEEK insulators. What you have there looks, from the image, like a Tsunami clone. I only paid $20 for my authentic.
https://www.fasttech.com/p/8014108 would be an easy, inexpensive option, if you aren't ready to build clapton wires. (also if you are lazy, like me.. lol)
3m = roughly 20 coils.(or more)
