Buying secondhand

This is more for those who aren’t on their first baby like I am, but all input is appreciated!

What items can/could/should I buy second hand? And what items should be bought brand new? I know for a car seat, that needs to be brand new for safety reasons. But I’m clueless on anything else.

We haven’t had a baby in the fam in a decade and I’m being a bit picky about the handmedowns. Not sure if I’m being overly dramatic but 10 years ago is a long time.