Newborn size vs 0-3 months

Officially in month five! Nesting has kicked into fifth gear and I’m scouring FB marketplace like it’s a desert wasteland. On the topic of finding baby clothes though, I’m slightly confused. The newborn / 0-3 mo sizing is slightly confusing and I’m trying to plan for it well.

Anyone have any advice on how much newborn sized stuff I should stock up on vs 0-3 months? It’s unclear how long baby will be in newborn sizes but I don’t wanna over/under stock on one. Just trying to map out how many pairs of sleepers/onesies/shirts pants I should get to start.

TIA - FTM 💕