You can get really good prams second hand on gumtree in good condition. I got a near new condition bugaboo buffalo for £100 (the owner paid 1000 for it 4 years previous) I barely use it as baby always out in a sling so I am so glad I didn't splurge.
I'd really not recommend buying reusable nappies before baby comes. Sign up to your local nappy library and you can buy lots of different types. Some people spend £500 on a bundle only to find it doesn't fit their baby properly.
The reusable cheeky wipes are fantastic, if you're going down the reusable route.
Newborn clothes lasted my boy a week, I bought a bundle of 10 for £1 each on gumtree and it was all I needed.
Sling - I have second hand ergobaby 360 which haven't used yet, and got fabric sling in babybox but they're machine washable so could get 2nd hand and wash at high heat.
You'll probably be gifted lots of clothes and blankets but often these are surprises as very few people will ask if there's anything you actually need! So have some 0 to 3 month sizes. Worth keeping an eye in m and s, sainsbury etc for some really nice and often reduced vests and babygros. I personally wouldn't bother with outfits.
Baby sleeping bags are great. My boy loves them. I have 3 newborn size ones which I circulate (often wakes up with sick stains etc)
Our second hand (actually borrowed) snuzpod crib is great you could get that on gumtree.
Tbh only thing that NEEDS to be new is a carseat. I like our joie igemm, almost got the 360 but you can't detach that from the car. And the docking station was definitely worth the money as such a faff putting it on with the seat belt.
Also bought mattresses for crib and pram from little green sheep. Get plenty sheets for crib, we have 8 and go through them regularly!
I got Dr brown electric steriliser new, some random website was selling for 70 instead of 100. I really rate it.