I tend to give gifts at a baptism/christening - for a child, usually just a small token (eg a small Bible Story book, like Noah's Ark) and a card. For an adult baptism, I would probably go along the Christian gift line but give in accordance to how close I was to them, like a birthday gift.

If this is for a child, be aware that the people in the Church usually say en masse that they will help to impart Christian values to the child as he or she is growing up. Something to be aware of - you can, of course, remain silent here if this goes against core beliefs or ethics.