Buying stuff for baby

When did everyone start buying stuff for baby? I’m 12 weeks 3days today and I’ll be finding out at the end of the month the sex of the baby.  I know that a baby needs a lot of things so I figured I would start early and just get a few things here or there or if I saw a good deal but I’m just worried that I might jinx myself. I don’t know. I guess I don’t know when is the right time.