K.A.
I used a few giudelines when deciding. How much did I use it. If it was all the time, unless it was completely worn out, I kept it. Would I use it for children of either sex? This one was a bit grayer. If the answer was no but it was something that I used endlessly then I kept it anyway because you may get another of the same sex. Have they made improvements to the item since I last bought it that would make it worth getting the newer one when we had a new baby? Even if we used it all the time if the newer versions have improvements that I really liked but since my child outgrew it it wasn't worth getting the newer one I got rid of the old one. I pretty much kept all the clothes unless they were worn out and then I'd just throw those out. My daughter has worn outfits that belonged to her brothers quite a bit. How far apart they are also has a factor in things. I have 3 kids, 2 boys and then my girl. There is 3 years between my first 2 and then my third the boys were 8 & 5 so a really big age gap in terms of something things.
I do have things I have kept and used for all 3. I am holding on to some of them still in case we have any more, just in case.
We replaced a lot with our third because she was a girl and because some things were really beaten up after 2 boys before her.
I would look at what you've got and decide from there.