How can i save money for my 6 mth old child and the one im expecting for their neccesities?

im 17 and their dad is 18 and works full time plus overtime. he gets paid about 1600 a month and we pay rent, water, light and food. we get left with about 200 for the neccesities for my 6 month old and for our own neccesities. we dont buy things we dont need. how can we find ways t try and save money. and please no offensive comments i really need some help.