None of us can say what is good for YOU personally - despite the fact that people have lol - because we are NOT you and what works for each of us is specific to us alone.
I smoked ultra lights, a pack a day, and 24mg was way too high - 12mg is much better for ME.
Your body will tell you what is best for YOU, experiment with levels (buy small sample sized bottles to save money) until you find a good one.
The advice on what is 'too much' is right though; headaches, shakes, feelings of anxiety, anger, hiccups, indegestion, 'the runs' are all indicative of too much nicotine.
Too little nicotine will have you craving smokes.
People often recommend 24mg as a starting point, nothing wrong witht hat advice, but there is no 'cookie cutter' spec that goes by how much you smoked; you just have to find YOUR 'right' level by experimenting. That can be fun too - you can taste new flavors while you're at it

GOod luck!