What to keep?

Mamas of more than one baby: what did you keep from your first? Did you end up using what u planned to resue or ended up repurchasing more anyway?

My baby is just about outgrowing his newborn-3mo clothes/swaddles, etc. I’m having a hard time deciding what to keep since we are planning to have another down the road but obviously don’t know if it’ll be the same gender or not. Should I get rid of most or keep most things? And until what age?