[gregjor]

By a wide margin: diapers. Little cloths for wiping up spit and drool a close second, though if you use cloth diapers they can catch the mess at both ends.

Car seat required, I always got the higher-end models with the best safety ratings. A good stroller as well, preferably the kind that work with the car seat.

Children mainly need your time, attention, and lots of patience. They generally don't need a lot of things until they get older, at which point they will tell you what they want.

Authority: I raised three children who started out as babies and toddlers and all lived to adulthood.