Probably a safe amount would be $25.00. Find out what the baby will need. Many people buy a big bag of diapers and these are appreciated. To be different, a nice personalized piggy bank made of pewter is a big hit in this area.
You should expect to spend about 50 to 100 dollars at the most. You should buy diaper bags or like baby clothes for the baby. You can also buy other baby gear.