How much weight you should put on during pregnancy depends on your weight pre-pregnancy. There should also be considerations if you are carrying twins or triplets.
A healthy BMI range is 18.5 - 24.9. If you are within this range you should expect to put on between 11.5 and 16 kilograms.
If you have a low BMI, below 18.5, you should gain between 12.5 and 18 kilograms.
If you have a high BMI, above 25, you should gain between 7 and 11.5 kilograms.