I was 1.5+ pack of 18mg per pack cigarettes per day and started with 18mg now heading toward 12mg.
As a total generalization, many people on the forum seem to start with...
Full strength cigarette smokers - 24mg, might need 30+
Lights smoker - 16-18mg, may need 24mg
Ultralights smoker - 10-12mg, may need 16-18mg
But satisfaction also depends on how much you vape, how often you can vape, how satisfying your e-cig hardware, juice flavor and TH is to you etc etc etc
If you are happy at 10-12mg then it's probably right for you. It's a reasonable amount for an ultralights smoker unless you have to wait really longer between vapes.
It is hard to compare the absorption of nicotine from cigarettes and e-cigarettes. Much gets wasted with both - cigarettes smoke away when you are just holding them, ejuice nicotine may be less absorbed than smoke nicotine, the drag sizes may be different, the amount of vapor you see on exhale depends on PG/VG etc. If it feels right to you then it's probably right. I recently started vaping more than I smoked so I plan to try one step lower nicotine level of my favorite juices.