I put on 18kg with my first and 16kg with my second.

It took about 12 months untill I had lost most of the weight. I've always been underweight so I wasn't fussed about putting weight on anyway.
I have a g/f who bragged about only putting on 4kg, but she smoked her entire PG.

I guess if you eat well, not too much junk, then your body will do what it needs to do to get you through growing a healthy baby.