Baby List, 4-6mo
It's been there months since I posted Baby List, 0-3mo. So, what's new? A lot, but also much less than you might expect. The big difference is that in the run up to your first baby, you have time and you don't really know what you need. Once baby arrives and you're in it day to day, it's much easier to figure out what you need now and in a few weeks. Which is to say, you don't need to bulk buy anything they way you were tempted to before babé arrived.
That said, there are a few things that were useful or are changes from the 0-3 list.
Bassinet - Both of ours were mostly useless by month four. There was a brief regression at once point where we pulled the bassinet back into play for a couple of days, but then phased them back out. One's gone to a new home, the other is in a closet until I figure out what to do with it.
Clothing - We're about 50/50 donated and purchased clothing. For night time we really like the design of Günamǔna's pajamas. I'm sure many other folks have the same design, but they're the ones we saw first. There's a zipper that runs from one ankle, up, across the crotch, and back down to the other ankle. It makes changing diapers very easy. More so than the diagonal shoulder to ankle zips.
Speaking of zips, snaps, etc. In month 0..3, your baby is probably chill enough that the fasters make little difference. By 6 months, at least in our experience, baby can move, grab, wiggle, twist, and turn. And they'll do all of those things while you're trying to get their leggings on and off. Zippers are easy. Snaps are hell. We have one very soft, very nice onesies that has twelve snaps. They're always annoying at this point. So, Zippers. Idk about magnets. Velcro is great if you want to definitely wake your baby up.
Sleepsack - Sleepsack are what come after swaddles. Good news, they fit from roughly 4mo to 24mo, so you'll get a lot of mileage out of them. We've tried two brands Woolino and Günamǔna. I like the Woolino material (wool+cotton) and design better. Specially, the design makes it easy to get baby in and out of the sleep sack during night diaper changes. And as a bonus it has a cutout allowing it to be used with a stroller harness.
Toys - You're going to start to have more toys. Maybe you buy them. Maybe they just show up. Maybe somebody feed something after midnight and like gremlins or tribbles suddenly they're everywhere. For months all the toys fit into one small bin. Then it was two. Now it's three. Plus there are two playmates, a Fisher Pierce and a Lovevery. And there's a large playpen semi-permanently constructed in the living room.