I found as soon as I asked people if they could recommend anything to buy and what type of things I would need they would say they have X,Y,Z lying around and would I like to borrow it.
If you are close to DH's family there is nothing wrong with asking, just ask if they have anything spare that you could borrow because you don't want to waste money on something that won't get used or used for such a short time. Most of the time people are glad to get rid of baby stuff.
Generally though babies are only as expensive as you make them, you don't have to buy lots and certainly not new stuff. I spent a fortune on my DS only to realise that I did'nt need a lot in the end and passed on loads of barely or unused stuff.
If I had to do it again my must haves would be:
Travel- Pushchair, footmuff, raincover, sling and car seat
Sleep- Cot, matress, 2x baby sleep bags, 2x sheets and 2x swaddling blankets
Cleaning- 10x Fleece babywipes, Bath support, 4x flannels, Bar of goats milk soap, changing bag mat
Feeding- Breast - 12x muslins, Lansinoh, 6x washable breast pads Bottle - 6x bottles, 6x teats, steriliser, 12x muslins/bibs
Play- Travel toy arch, rocking bouncy chair
Clothing- 5x Babygro's, 5x vests, 2x cardigans, 2x hats, 2x scratch mitts
I know it looks a lot but really it's not, anything else is just preference IMO.