What should a newborn wear to sleep?

Matilda

I’m currently 26 weeks and trying to figure out what my baby boy will need for clothing in his first months. I live in Minnesota and am due February 25th so for his first 3-4 months it’ll be pretty cold out. Im a first time mom so I’m a little confused as to how much they should wear and how many clothes we need. Do they need to wear onesies under their sleep suits? And do you *need* sleep sacks/swaddles to be warm at night or are they more of an “extra” thing? I’ve heard a lot of different things about that. Also should I spend money on a baby jacket or winter gear like that and if so would it be better to buy a newborn or 3 month size? I really need help figuring this stuff out 😅