MOST of what folks are buying today for babies is not necessary, strictly speaking. And if you're trying to stack sats, buying used and/or being very minimalist is perfectly fine.

Underrated - keeping a decluttered house, kid-friendly house. Not a ton of toys and kid stuff around. Make it so that if the kids are rummaging around, they won't find things that hurt them, or that they could damage.

Find other parents with kids the same age. That's so valuable, and it can be so fun to just hang out with people going through the same thing.