You know the one baby toy I’m totally getting for anybody I know who ever has a baby? The best baby toy ever? This thing. It’s a ball with holes in it that rattles when shaken. My little guy can spent hours holding onto it, looking at it, and trying to put it in his mouth. Five motherfucking American dollars.
We do like the play gym thing with the mat and the arcs the toys hang off. He’s been practicing reaching on that. And my parents got him the Kick and Play piano thing, which is the most annoying thing in the world but he LOVES it, and it was amazing to watch him figure it out immediately. Not necessary, but if somebody wants to get you a toy, it’s a good one.
And you need, if you have a big enough house, a place to put the baby in every room you’re in. Our first few weeks we kept hauling the Rock n’ Play from room to room - that sucks. Get one of these $25 bouncer things - very easy to clean, cheap on batteries (they last forever), huge play value. He loved it then and still loves it now at 6 months. I think ours was even a little cheaper than that one - that’s the one my mom has. Because you are gonna want to be able to put that little scamp down, especially if you get stuck having to pump. Trust me.
And consider cloth diapers. We use prefolds and covers and it’s so easy, cheap, and we never have to remember to buy diapers. You’re doing a ton of laundry already, it’s not much more. (I say that in every baby thread but seriously - it’s not really a hassle, it seems to be better for his skin, it’s super cute, better for the planet, you can even resell them once you’re done, etc.)
We needed a TON of receiving blankets because ours is a spitter. Thought we had plenty, had to go buy more.
ETA - when he’d cry and cry, developmentally, in the “fourth trimester”, the only thing that would stop him was putting him in the bouncer and bouncing it with your foot. Worked every single time.