We bought pretty much nothing, though we already had a roomful of stuff from our older child. Plus dd2 came with an absolutely unbelievable amount of stuff from her foster carer - 5 sacks of clothes and 7 huge trugs full of toys. I actually felt really oppressed by the amount of stuff and had to think through what to do with it all. It's not easy as you're told very strongly to keep the stuff they're familiar with, but I was never allowed into her bedroom at the fc so didn't know what that would be.
The clothes were easy: she grew out of them long before she got to wear them all. The toys I circulated round till I was sure I knew what she really liked, then I got rid of the rest. There was other stuff, like a big wall painting of a blonde fairy that tbh I got rid of because little black girls have to deal with too many blonde fairies as it is. And there was a box of jewellery and other gifts from the fc family that I have kept for her in her memory box.
A couple of things made me cross: one was that there was a particular blanket that I just packed away for a couple of weeks. When I finally got it out and put it on her bed she just fell on it, and I realised it was her 'special blanket'. Why on earth didn't the fc tell me that? I felt so sad and guilty that she had had to cope without it. Its significance was NOT obvious in that mountain of stuff.
The other thing that infuriated me was that there was a box of gifts from the birth family, that the fc held onto for about a year to 'make sure I get my visiting rights'. She had blackmailed another adopter in this way before. When I finally got it (after much fighting) it was all just slung in a cardboard box, full of dead flies, with no notes showing who had given what. It makes me so cross that I had so carefully preserved the special gifts from the fc family, but the fc couldn't give the same respect to gifts from the birth family. I don't KNOW which will be more important for dd2 as she grows up, but I'm guessing it will be birth family rather than fc...
Anyway, that was a long-winded way of saying that even little issues like what teddy you put in the cot can be fraught with meaning when you adopt. Allow yourself to buy a couple of special or specially useful things, but be careful not to overwhelm your new child with loads of new stuff.