U can cross one pair of mittens off the list.
It depends on the stuff.
Dont buy toys unless you rally, really have to have a specific thing. Toys just appear. And breed.
You really cant have enough singlets, socks things like that.
Also remember people may not have the same tate as you so if there i something specific you were after, and its not the sort of thing you can suggest or ask for then 'd buy it.

Sizing too - the majority of clothes we were given were in size 00 or larger, so if we'd not bought anything DS would have had no clothes for 8 weeks, or DH would have had to do a mad rush.