You need a car seat, brand new or from a trusted friend only. If you need a cheap one, and don't find a good deal e.g. in with a pushchair, Joie is the brand to look at. There are some cheap brands which have poor safety records but Joie is good.
It is worth noting if a pushchair says it's compatible with Maxi Cosi, then it's also compatible with Cybex, Joie, Recaro and Kiddy. These all use so-called "universal" pushchair adaptors often sold as Maxi Cosi adaptors.
Don't bother with a seat which covers multiple age groups if you want more DC or one which comes with a multi-stage base. This is a false economy 99% of the time.
You will probably want some way to transport the baby while out and about. It's really fine to buy some cheap old thing and then change it later - you don't know what features of a pram are REALLY important until after you start using it regularly. Slings are also great, but a pram/pushchair is easier when you're still recovering from childbirth. You don't need it to be compatible with a car seat, but you might like it to be. IMO, choose your pram and car seat model (or preferred features) ASAP, then you can look out for deals or second hand bargains.
You obviously need to dress the baby. Don't go overboard. You will need short-sleeved vests (8-12) and something to go over the top of that, like sleepsuits or little outfits. Sleepsuits are 1000 times easier, so make sure you have at least 5. But you might like outfits too. Again, 8-12 options for over a vest is enough to start you off. Get a couple of cardigans or little zip up hoodies. Don't bother with anything you need to pull over the baby's head. THEN - clock where your nearest and most accessible source of cheap baby clothes is, whether it's Primark or Asda or Tesco and when you run out of clothes, simply go in there and buy another pack of whatever type of clothes you're finding the most useful in the correct size. In advance of the birth I'd only get things in 0-3 months and 0-1 month, or H&M 0-2 months. Newborn is miniscule and only worth having second hand. Tiny baby probably won't even be worn unless you have a premature baby. If you try to buy too far ahead in sizes, you'll often find seasons don't match up. FB bundles, ebay, car boots, NCT sales etc all great for clothes. I would not bother with anything hugely seasonal like sun hats, snowsuits, because you can just get them as and when they are needed, which might be never.
The baby needs a safe place to sleep and appropriate bedding. I'd get a couple of cellular blankets and maybe one of those swaddle things if you would like to try one. If your baby likes it, you can get a second to wash and then start looking for more second hand.
You need somewhere in mind to put them down during the day. This might be the pram top, if it's a carrycot, or a blanket on the floor if you don't have pets. Or you can get various options - bouncers, swings, travel cot, high chair with newborn attachment. Again, it's best to keep it simple and/or second hand - your baby might hate what you buy, and it can be helpful to have the option to try them out in it in advance. Don't use a car seat for this, it's unsafe.
Lastly you need a way to change them and wash them and all the bits to deal with the various stages of that. If you get baby towels, make sure they're thick enough to be warm and useful. I like the look of the Shnuggle bath but both DSes have preferred to bath with their dads anyway!
I love muslin cloths and find them so useful. I would recommend you get a couple of packets as you can always buy more. It's useful to have an accurate thermometer to help quell those new mum nerves about temperature. And get some calpol in before the first jabs.
You probably do want a small, unobtrusive light for night feeds and/or changes, if you have a bedside lamp, that works fine. Anything dimmer is no use for a change because you can't see what you're doing, but a nightlight kind of level is OK for feeding and general checking on the baby.
IME you don't need anything else urgently - everything else can be got as and when you find a need for it, which, again, might be never. Try everything you can before you buy! If you think your baby might like white noise, try playing some from youtube.