Some items are essential, such as bottles, nipples etc. Some, you really should have, such as a bottle sterilizer, and some are just nice to have items. Although some are not essential there's no doubt they can make life much easier for the busy mother, especially when out and about or traveling with a young child.
Bottles and Nipples
It goes without saying that these are essential. Buy large bottles rather than the smaller ones, as you will need the larger ones as your baby grows. Make sure the teats are suitable for your baby's age. Buy teats with a smaller flow for young babies and vice versa. Also, make sure to replace teats regularly. Lastly, always buy good quality.
Bottle Sterilizer

Another essential. There are several different types you can buy; ones used in a microwave, electric steamers and electric/microwave combinations. Buy what you think is most suitable and on what you can afford. The one picture to the left is an electric sterilizer you can buy from Wal-Mart.
Insulated bottle carrier
These are bulky but useful for keeping made-up bottles cool until needed (for up to five hours).
Formula powder container
Means you can just add formula powder to bottles of cooled, boiled water when your baby needs feeding. A bit fiddly if out in the open but a cheaper option than the insulated carrier.
Baby flask
Use the hot water from the flask in the container provided to warm up your baby's bottles or jars.
Cartons of ready-mixed formula
Great for your changing bag, these don't need keeping cool but are a little pricey. There great for when you're traveling as preparation is not necessar
Car bottle warmer
Plug into your cigarette lighter for warm bottles on the move.
Travel sterilization bags
Two types are available: one with drawstrings for cold water sterilizing with tablets and another that can be used in the microwave up to 20 times.
Muslins
Cotton squares to protect your shoulder and wipe away baby dribble.
Bibs
Plastic-backed ones are good for babies who guzzle their milk, to stop it getting under their chin and making them sore.
Dishwasher basket
Useful for keeping together all those fiddly bits of equipment that need washing before being sterilized.