I bought only 0 - 1 mth items (0 to 3 would have swamped her) and loads of muslins (15 or so, not all muslins are equal, next have the best ones) to allow for gifts (not including bottles etc). That normally takes them up to 9/10lbs. She was in them until 5 weeks ish (born at 6lbs 13oz) and even if I had received no gifts I would have had loads of time to buy more clothes.
I got a .5 and 2.5 for bag, 3 cellular blankets, 3 sheets for the next 2 me crib and 3 towels (figured 1 in use, 1 drying and 1 in wash)
You don't really need bibs etc to start with and we were given loads as part of sets. Mitts were pointless, they just came straight off so I had maybe 10 sleep suits with integrated mitts, 10 vests (mix of long, short and no sleeves). I only changed her clothes once a day for the first few weeks as she was hysterical.for the entire process, that's if she wore any due to the 33 degrees in the flat.
She only wore 2 hat's and that was in the hospital and leaving it, but again, she was born middle of June so it was very hot for a long period after that.
I got gifted loads of 0-3 and 3-6 I've not had to buy anything else yet except tights and a couple of pairs of shorts to cover her nappies when wearing dresses.
Other than stocking up of nappy changing and feeding stuff if not bf, if you have what you need for the first month you'll probably be given a lot of gifts for the later months or have time and fun picking out more stuff.
I hope everything goes well.