We were temporarily in a tight spot when we had DS. Our friends were all buying everything ever invented for babies, and we really had to think, which at the time, I felt really guilty about. We didn’t buy much, and in hindsight, I’m glad.
Things we loved, and invested in, included:
A well researched travel system which suited our needs (& still carries a three year old when needed)
A stretchy sling
An Ergo carrier
A decent backpack with pockets, which we used as a change bag and then day bag
Gro-bags (bought later)
Vibrating bouncer chair
Tripp Trapp (bought second hand and still used by nearly six year old at the table
Giant muslins - laud over towel as change mat, feeding cover, lightweight blanket, floor mat.....
Decent feeding bras (if b/f)
Breast pads (if b/f)
Nice lounge wear (in case you can’t wear normal trousers after delivery/ need to answer door when you can’t get dressed etc.).
Sleepsuits with integrated mittens
Progress to soft footed trousers or dungarees
Bath rest (if doing bath time alone)
If you are looking at a cot, buy a corned, and see if it can be put beside the bed. We bought an adjustable height cot bed, that DH ratcheted to our bedframe. MIL made a solid bolster to block the gap at the back of the cot, when the cot mattress was pulled against ours. We then covered the bolster and matters with one sheet to prevent any space forming. The cot bed is still in use by DS2 six years in (he’s 3)
As others have said, many things can be bought second hand.
Things I never really used:-
Breast pump/ sterilising stuff
Most of the blankets we were gifts (stuck to 2-3 decent ones)
Plastic high chair that trapped food