Whenever one of my friends gets pregnant they ask what the best stuff to get. If you're a minimalist or do not want to spend a lot of money, these are the things I consider basic and necessary.
Diapers: I don't care if you use cloth or disposable, but your kid will poop on you if you don't buy something.
Onesies: You might want to just get a bunch of white ones. Especially if you have a girl, pink onesies never match pink pants. It's an industry thing meant to drive new moms nuts. But if your onesies are all white you've beat the system.
Pants and sweaters: For the cold. Be colorful; white baby pants are silly.
Crib: So the baby has somewhere to sleep. They outgrow the co-sleepers and bassinets, so if you want to save money go straight for a crib. If you get one that's convertible into a toddler bed you can use it for years and years!
Warm pajamas and/or Baby sleep-sack: for winter sleeping. Because babies can't use blankets.
Ergo carrier/stroller- one or both. Our kids kind of hate carriers. Some people only use carriers. If you buy a stroller consider whether you will have to personally lug it around. The big tank ones are for SUV moms (they carry all your stuff!). City moms like lighter and more versatile ones.
Fire and smoke detectors.
Car seat if you have a car. And check that it's installed properly.
Not strictly necessary but very helpful:
Wipes: Actually this is necessary. You could use wet paper or washcloths but what a pain. Just buy wipes.
Diaper bag: I could have listed this under necessary also, but I guess theoretically you could throw a bunch of stuff in your large purse. For lots of reasons it's better to get an actual diaper bag. I got a manly looking one so I could make Kevin carry it.
A book about baby sleep: This one: http://amzn.to/1BiGqlo (or Dr. Ferber) It doesn't actually matter what sleep book, but when you're exhausted, some sort of guidance will save your soul.
Sound machine: We like these so much we bought two, one for our room. http://amzn.to/146wyym
Highchair: Somewhere for the baby to eat once he or she can sit up. We like ours because it's small to store and travels well http://amzn.to/1xEGRaz
Bibs: Babies drool and spit up and if you want to avoid changing them every few hours, bibs will save you. Relatedly, burp clothes for the first 6 months or so. You can use anything but it whatever it is will get wrecked.
Here are some I don't like. There is a thing called a burpy bib - it's a burp cloth and bib in one. I prefer mine to be separate but to each their own. These bibs seem like a good idea, but they are not- they bump into everythinge: http://amzn.to/1wNuEcs.
Bath soap for babies.
Diaper rash cream: One of my kids never had diaper rash though and the other one only a little, so one tube should suffice until you know how sensitive your baby is.
Baby nail trimmer.
Thermometer (you might want a seperate one for baby)
Good to have:
Baby bathtub: You can give them baths in the sink until they're able to sit up but this might be super inconvenient.
Baby bath towel. The little hood thing is kind of helpful. Plus their cuteness helps you tell the difference between their towel and yours.
Changing table: A lot of people change their babies on the floor but I like being able to stand at a comfortable height and having all the stuff in one place is convenient and more hygenic.
Swaddling blankets: But! I found the generic ones kind of useless because they were too small. I enjoyed the extra big Aden + Anais muslin swaddle blanket. They're a fun luxury but really only useful for the first few months.
Big plastic tubs: So if you get a lot of stuff you'll want to store stuff that the baby isn't ready for so it's not in your way. (Also, if you plan on having another baby, you'll want to store the stuff that baby this baby outgrew.
Breastpump: They're covered by insurance. This might rise to the level of necessity depending on your situation.
Baby bottles: If you're not going to nurse or going to pump.
Formula: If you're not going to nurse. Be warned, it's expensive and once you get involved with formula you might be committed until the baby is 1 year old.
Baby don't really like anything for a while. Some newborns appreciate a pacifier but the controversy here is out of control.
Once they can grab stuff the only thing they want is to chew on stuff. Sophie the Giraffe is good. A rattle can be chewed on or is entertaining.
Eventually they can bat at stuff and will enjoy an overpriced baby mat/ baby play gym. (Anyone want mine?)
I also recommend bath books, not for use in the bath, but because they can chew on them and not ruin them.
They don't usually like real toys until about 6 months when they can sit.
Moms, what else did you think was necessary?