My must haves are a cosleeper, babies like to sleep with you, not in a basket next to you. Muslins are helpful for all sorts, I place one on the bed for leakage and night feeds etc. Sleep suits with built in scratch mits, regular ones do Not stay on lol. Breast pads, lots of them. Slings are far better than carriers! Hubby got a carrier and it was useless until our son was bigger, no head support, a pain to get him in and out etc. Decent car seat with base as that will fit in any car was extremely useful for us. Pram with good suspension, otherwise they get every bump and keep waking up. If you will have to pump, find one you get along with. I got an expensive one and once my nipples changed from feeding I don't get on with it at all and havnt used so that was a waste of money. Nipple cream is sooo helpful in early days when milk comes in. Breastfeeding Hurts, a lot, you will bleed and scab and want to stop, but grit your teeth, stick with it and your body adjusts then it becomes easy!
Also for after birth hubby got me some tenna lady pants, they were amazing for controlling leaks whilst still bleeding. They are scented so I put a maternity pad in them, made life much easier and more comfortable. If you pack snacks try to take light things that won't make you sick in labour, but afterwards eat whatever the heck you like as you will be starving and you deserve it.
Things I didn't need were lots of cloths, they grow out of them sooo fast! Baby lotions and potions, he's 12weeks and so far have not used any of them (water alone is best). However I do occasionally use sudocrem. Mits, shoes etc not needed or used, hats don't stay on unless wooly, slightly elastic. Dummies, we have not used as havnt had the need to.
I have found that keeping it simple is best, then buy things as you need them if you would find anything else helpful along the way. We have far too much 'stuff' that people gifted to us and we havnt used so it's now just clutter and in the way.
I exclusively breast feed so nursing tops and bras are a must, I find the clips on tops snap easily so be careful when choosing.
A tip that a nurse gave me was to not mix breast milk and formula, especially in early days as your colostrum coats the babies stomach with good stuff, using formula can destroy that and lines it with not so good stuff and makes baby more prone to being sick etc (something along those lines, I can't remember exactly) . So if you do plan to bottle feed at all, try to wait a little while. My boy is only breastfed, so far he's never had colic and has only been sick twice! He's 12weeks now.
I also regret not having any professional pictures done as a newborn, they grow really fast so take in every moment

Good luck ladies, becoming a mum is the most amazing thing!