A lot in the first 3-6 months (spit up, diapers, etc.). Then it starts to depend on your kid, I feel like. And seasons, of course. Then they eventually start running around and wearing holes in things. And may play sports so you need gear for that.

I'm doing it wrong, apparently

I would love if that were true, but in my areas of research it sadly hasn't panned out. So now I'm on multiple platforms just to keep up.