I answered 12 to the poll, since that's pretty much where I'm at. But for someone starting, unless they were a very, very light smoker, I think they'll need a higher level.
I started at 24, and couldn't get off the cigs. I cut way down, but after meals, I'd get cig cravings and vaping just wouldn't stop them. Then I got some 30mg juice. As soon as I did, quitting cigs was easy. I'd use the 24mg juice as my "all day" and after meals, I'd drip the 30mg juice.
After a week or two of doing that, not only was I cig free, but I found that I rarely needed the 30mg juice anymore. The 24mg was enough. I didn't buy a lot of 30mg juice, and I still have most of what I did buy, because I just didn't need it for long.
Now I'm smoke free for over 5 months. For the last month or two, I've been vaping 18mg juice. And I just received a 100ml bottle of 12mg. What I'm vaping right now is roughly a 50/50 mix of the last of my 18mg and the new 12mg. So assuming my non-measured mix is actually 50% of each, I'm vaping at 15mg. When that runs out, I'll be vaping 12mg. And if the switch to 12mg goes well, then in a month or two, when I have to order more, I'll try to move down to 6mg.
If I can get down to 0mg, I'll do that. If I find that I get to a point where going lower isn't working, then I'll stay there, but I'm hoping to get off the nicotine addition altogether. If I can do that, then I'll see about putting the PV aside. It would be nice to be completely free.
But if I vape the rest of my life, I'm OK with that. If I find that going below 12mg doesn't work for me, I'll do that. I'm so happy to be off the cigs, the rest doesn't worry me much.