I haven't tried giving monetary gifts during my two inaanaks' baptism but rather gave them something they'll need later on like clothes, shoes, toys etc. But my aunties and cousins who went to our house and saw my baby for the first time, each gave Php500 at the minimum. And then my mom told me to save those money and use them only when baby turns 1. And I followed her! Haha used them to add in our budget for her 1st bday. ;)
It really depends on how much money you are willing to give to the person :) As long as it's from the heart, I think they will be grateful for it :)