I used to work in a baby stuff shop, and I have 3 DC.
I don't think the super expensive car seats are worth it personally. You can spend £450 on a top end one with a rotating base etc or you can spend £120 on a basic one with optional £80-100 on base, and just rotate it however you like in the house which is where you actually put the baby in and out of it anyway. They are just as safe (if you buy a decent brand with good side impact protection etc). And actually, even the brands that usually do poorly for safety ratings tend to have a fairly decent safety rating on their infant seat, because the infant carrier being rear facing is extremely safe to begin with.
(There is nothing wrong with the expensive ones and they do have different features. If the feature is worth the difference in price, then fair enough - but you should know what you're paying for.)
I didn't use swaddles or scratch mitts, didn't like them.
Snow suits utterly hated these, faffy pointless things. Just use blankets.
Don't get a massive bundle with a million extras on a pram - it's usually cheaper to buy the pram unit itself separately and then you can pick and choose what accessories you actually want. Universal raincovers are generally fine, though get one from Boots, supermarket etc not Amazon, you don't need a matching changing bag (unless you want to, but again, know what you're paying for). Parasols are totally pointless, rarely stay up and don't work properly. If you are going somewhere sunny, a UV net or shade is better. In the UK, you can just angle the buggy or place it in the shade. You generally need the proper car seat adapters, if you want to use the car seat on the buggy. Maxi Cosi ones take most brands (Cybex, Britax, M-C, Nuna, Joie, Besafe, Avionaut) not just the short list that they usually say on the website, but it has to be an "infant" type - things like Joie 360 Spin can't go on any pram. You can get away without buying a carrycot, if the pram has a lie-flat (esp parent-facing) mode, but a carrycot is a bit nicer, more contained and has a proper mattress - some are even approved to use for overnight sleep. This can be helpful if you plan to do a lot of walking or you want to use the carrycot in the house, or travel when LO is younger.
Purpose-built co-sleeper cots are generally faffy, don't last very long and not that good. Get an IKEA cot, or any cotbed and convert it instead if you want a co-sleeper type cot.
Actually IKEA furniture in general is brilliant for babies and SO much less expensive than the overpriced nursery sets. It used to boggle my mind seeing people come in and spend 3k on a nursery set when you could have got the lot for a few hundred pounds down the road at IKEA!
Modern style baby bouncers with the teeny tiny round seat are not as good as the old fashioned ones which were huge. Only the Baby Bjorn one (and copycats) are like this now - these are worth having, but they are more expensive so might not be worth it. If you want a cheaper style, it's worth getting something like a rocker, or a swing with a motor. You can wait and see for these if it's something that seems useful for your baby or not. It is helpful to have a "parking space" for the baby in different areas of the house, before they can crawl. I think personally the laid back bouncers/rockers etc are better for them than seats like the Bumbo. I am not keen on the pillow things like Snuggle Nest - I think they are misleadingly marketed (and too expensive).
If you want to use a baby bath, the Shnuggle one is meant to be the best and if you need to use an in-bath bath support, the Angelcare one is the best. Before you buy any kind of baby bath insert, try kneeling down next to your bath (preferably early in pregnancy without a bump, or get your partner to!) for 10 minutes leaning your arms into the bath. It is surprisingly uncomfortable. Any kind of tub that you bring out and fill with water is also a bit of a pain. To be honest, I found the easiest way to bath babies is to stick them in the bath with an adult (I made this dad's job otherwise they just wanted to breastfeed) or bath them in a sink.
For slings I'd def recommend a sling library or sling consult rather than going in blind or buying whatever the most recommended model is (which is always Ergo - big marketing budget). Personally I'm a fan of a stretchy wrap for the first 6-8 months and then a soft structured carrier, but a more basic one, not the ones they have now with loads of different modes, but everyone has different preferences.
In general you can get SO many things second hand, doesn't need to be new. (Car seat, dummies and bottles yes). Babies use things for such a short time.
Also, think about whether there's an adult version which is cheaper (e.g. towels - you don't need a baby-specific towel, it's just a smaller version of a normal towel) or an own-brand which is fine (e.g. bottles, dummies - you can get all kinds of brands, Nuk, Mam etc or just get a bog standard Tesco/Boots' own.)
If you are going to buy things new, consider a brick and mortar store especially for expensive/complicated items. Best is an independent nursery specialist, second best is John Lewis/Mamas and Papas, everything else (Smyths, Halfords, Boots, supermarkets) are all a bit hit and miss but still generally easier to deal with than online. The recommendation for only new mattresses has been withdrawn, but it can be nice to have a new one anyway.
Think about washability of things - don't buy a pillow support thing which is sponge clean only.
On this note, get 2x waterproof mattress protectors for your bed. Babies are leaky, and so is late pregnancy/postpartum. Get the nicest one you can as we only felt confident to ditch them once the youngest was over 18m.
Think about whether you'll really need something literally from day one - if not, you can always wait and see if you want it or not. You can save a huge amount of money this way. If you have an urge to shop anyway, scratch the itch by researching and create a list, spreadsheet, amazon wishlist etc.