A couple things to consider:
I am fine advising new people to go sub-ohm on a regulated device (like the iStick). You get more clouds and flavour which will help make it a more fulfilling experience and help resist the urge to smoke.
One thing to consider though, is that with the Atlantis in particular you need to inhale directly into your lungs. This isn't something tobacco smokers are used to and it's more similar to the inhale you use for dry herbs: you need to expect this and be comfortable inhaling that way.
On the Atlantis in particular, they have a 1.0, 0.5, and 0.3 coil:
- I wouldn't recommend the 1.0 because it doesn't lend itself well to the way you have to use the tank.
- I find the 0.5 coil needs ~47W. This is at the upper limit of the iStick 50W's capability and i'm not fond of pushing things to their limit, your call.
- The iStick 50W can't hit the wattages needed to use the 0.3 coil.
I would recommend a Subtank with the 0.5 coil. It works well, I find, at 27W. The draw is a lot more like a cigar - the clouds are thicker and more flavourful. This is especially true compared to the Nautilus.
I like the Nautilus a lot, it's one of my favourite tanks. I recommend it to a lot of new users but because your device can fire a Subtank well, and the Subtank is superior in nearly every category, I can't recommend it as a #1 choice.
Considering your budget (assuming similar to what you've asked), experience in smoking, and especially the fact that you don't currently smoke but are trying to avoid the urge, my #1 suggest would be an eGo-One starter kit.