shelivesthedream and milennialworkerbee pretty much nailed 90% of it.
I will add my $0.02 to the mix:
-Ask that everyone refrain from buying outfits. People love to try and find the cutest outfit to bring, and for both of our boys, most of the outfits people got us were too nice to wear, weather inappropriate, or they were already too big for. If people insist, ask they get clothes a few sizes up (6-9mo, 9-12mo). Its a fantastic feeling knowing you have a reserve set of clothes for when your kid grows and their wardrobe isn't ready.
-Even if you go with disposable diapers, get a pack of cloth diapers. There is nothing more absorbent out there. They make the best burp cloths, and emergency mess rags.
-A 10-pack of plain white onesies is far more useful than you would ever imagine.
-Sleep sacks are so much easier than swaddles. It's going to depend on your kid's temperament but our boys each escaped the swaddle in about 4 weeks. if you do swaddle, the ones with velcro are much more escape-proof than a traditional swaddle blanket.
-Consignment sales are a must. Buy a few sizes up, not what your kid needs right now.
-Converse to the above point - buy the equipment you need right now. Do now but bouncy seats, door jumpers, high chairs, baby gates, bumbos, utensils, etc. until you're about ready to use them. We saved so much money and sanity with our second by waiting until when he was ready for those items, because we needed about half the things we thought we would need.
-Finally, there are two things I recommend splurging on:
1) Car seat. Do not buy used. Do not buy the $40 seat. Buy something that will keep your child safe.
2) Not an essential, but if you can swing it or find a clean used one, a Baby Bjorn bouncy seat. Never ever did my wife and I think a $150 bouncy seat would be so worth it. We were appalled
when friends of ours bought one. We thought they $35 Fisher Price one was "good enough". It was not. In short - our second spent a good part of his day in the Bjorn and after 8 months
of regular use, it's still in A+ condition. We'll be able to reuse it for future kids and still sell it for $80+