I have a Nautilus 2. I like it, but it's a bit fiddly, and I know some people have had a lot of trouble with it. As far as I can tell the main thing is to learn just how much to tighten the coil- it's a bit more than you'd think it ought to be. If you don't tighten it enough the top of the tank will loosen it when you open it to fill it, and it will leak. Another tank that is similar, and can take the same coils, I think, is the IJoye ELF, but I have no personal experience with it.
Yeah, though I can't speak to the tank I have a Pico, and it seems like a good value to me. Here's another link (to just the mod, though they have the kit too):
Eleaf iStick PICO Simple Kit - $32.00 : Rocky Mountain Vapor, The Mountain top of Electronic Cigarettes . They have 30% off site-wide with a code they list on their front page, and that brings the cost for just the mod to just over $20.00. That's the best deal I've found on the Pico.
I agree about nicotine levels- the trend these days is toward dripping and sub-ohm vaping, so a lot of juice is only available at 6 mg or less. That's probably not going to be enough for you in an MTL tank. You'll need to experiment a bit to find the level that's right for you, but my experience has been that it's better to actually get a little more nicotine vaping than you did smoking, at first. Full disclosure: I like nicotine, and have been known to drip 18mg, even though it's a bit harsh.
It's also important to find juice you like, or at least don't dislike. There are some off-flavors in a lot of juice that really bother me, that other people don't seem to notice... taste in juice is a very personal thing, so you just have to experiment.
The other piece of advice I has is _have backups for everything_. Redundancy is really important. Equipment malfunctions happen, and they happen a lot to newer vapers who haven't quite learned the ins and outs of things, and how to troubleshoot. You never want to be in the position of not being able to vape because something broke, or you lost something.
If cost is an issue it's worth noting that you can find quite a lot of serviceable stuff that's a little out of date really inexpensively in clearance sales. I have a fair number of toppers these days, some still in boxes

, but I also still have a Kanger Aerotank v2. I don't use it much anymore, because I have things I like better, but in a pinch it would do, and you can pick them and other similar items up for a song these days. It might be a little old, but it's much, much better than what I started vaping on.