As i am underweight ,i would like to ask how many pounds is a good number to put on after every week?

i am weightgaining as part of a bulking up as my structure at the moment is skinny but toned (which can be okay but i want more) so i need to know how much is a good amount to put on.I have a fast metabolism and have an active lifestyle,Should i dum it down a little and be a bit lazy??