I know there are a million of blogs there that lists the "must haves" for moms - and there are a few for twin moms.. but after reading most of them, I still feel like there were stuff in the list that worked and didn't work for me, so here's my list.. hopefully some moms will find it useful!
These are the items that I felt like you need to purchase/prepare before you give birth (or shortly after).
Here's a little information about me and our living situation, which I think affects the things that you will or will not need.
1. Diapers - We live in the city, so we just purchased one newborn size box of diapers. We bought diapers as we need it, meaning, when we are almost out. Unless you live in remote areas where you have to travel far to get to a store, I think this is one advice I would give to parents - buy when you are almost out of diapers (not completely out of course!!) because you don't know how fast your baby/ies will grow and what brand you and your baby likes. We were lucky, our boys were not picky, so we were able to buy diapers based on what was cheaper. We also didn't have to buy a lot of newborn diapers because we met a former doula who had a lot of sample packs that she gladly gave to us (jackpot!!). We found that our boys outgrew the newborn size quite fast, and because we didn't "stock up" on diapers, we were able to switch sizes without having to deal with a lot of "leftover" diapers. Right now we are using the Kirkland (Costco) diaper brand and we are good with it.
There is also the option of cloth diaper - which admittedly I know nothing about. But I did briefly toy with the idea of using cloth diapers but after talking to a few moms and doing a little bit of research, the amount of choices and information overwhelmed me. But I think it's the same concept in the sense that don't buy a whole bunch of one brand of cloth diaper, try it out first, see what works for you and your baby.
2. Swaddle - after a few research and reading a few blogs, I decided to get the Aden + Anais Swaddle, it's a bit more expensive but it's SOOO soft and it's big enough that you have enough surface area to swaddle your baby completely. We received a different brand of cotton muslin swaddles, but they were not as soft. I also tried to get the "easy swaddle" types of swaddles, but we didn't really use it that much -- and it was more expensive (and less versatile). We stopped swaddling the boys at around 6-7 months (because they kept kicking their way out of their swaddles anyway) and even now we still use the their swaddles as a blanket during summer or cover for their stroller when they are taking a nap.
2. A Million Washcloths (used from birth) Ok, maybe not a million, but we definitely needed A LOT! Our boys were spit-up kings! The washcloth we got was from Asia, it was the terry cloth type of texture similar to this -- I loved this because 1. It was cheap and 2. It absorbs well. Problem with this is that it's a bit rough, so if you're particular about that or if your baby/ies are sensitive, then this might not be a good choice. We also got the softer wash cloths as a gift, they're from Babies R Us. They are definitely softer, but I find that they are not as absorbent.
3. Onesies / Clothes - because we had twins, the most common advice you'll get it to get a "premie" size clothes because most twins come out smaller and they usually come out earlier too. Our boys were born at 36 weeks and were 4&5lbs. We didn't buy premie-sized clothes before they were born, most of the stuff I bought were NB (newborn) size. I personally don't think you need to buy premie clothes before your babies are born, simply because you never know how big they are when they come out (and premie clothes are TINY!) -- But that's just me. We did however bought premie-sized clothes a week after they were born, but only because they were born in the winter and we found that because their clothes were a bit big, it would bunch up when we put them on their car seats. We did only buy 4 sets of premie clothes for them and they outgrew it in maybe 2 weeks - but that being said, babies are different, so ours outgrew their premie clothes in 2 weeks, but for some (especially those born earlier) it might be longer. Buy as you need them, get a few then if you feel like you need more, then buy more. Here in Vancouver, BC, the only place where I found premie clothes were at Carters. (PS: you can also find lots of good quality used premie clothes - I gave ours to another twin momma).
Under this category are also socks & mittens.
4. Bassinet - We didn't really buy this - it was given to us (I'm sure you can find cheap used ones too). But I used this A LOT. I would put the boys on the bassinet (yep, they fit one bassinet), before and after breastfeeding - we have laminate floors so I would just drag it closer to the couch so I can take them out and put them back while having a twin breastfeeding pillow around me. I found this more useful than our boppy pillow (which I never used).
Here I'd also talk about Bouncy Chairs & Swings only because for us, our bassinet replaced our bouncy chair in the sense that it was the place where we put our boys when we needed a free hand. We had two bouncy chair but only opened one to try it out - we used it for a bit but the boys were never really "into" it and it was too low for it to be a place where I can put the boys before and after breastfeeding. We never bothered buying a swing (even though most twin mom swears by it!!) simply because we didn't have room for it anymore (let alone two swings!!). We got by with just one bouncy chair (that we barely used) and no swing - I also used my wrap and carrier a lot when they just want to be held.
5. Burp cloths - The burp cloth we used are not the same ones as the one being sold here, it's similar to the receiving blanket that they use in the hospital, they are big and pretty absorbent. I can't really find the exact same one we have (again, got it from Asia), but I think it's similar to this . You need a big one so you can drape it on your shoulder when you burp your baby.
6. Nursing Bra - I only bought one nursing bra and used it when we went out (I mixed fed, so I didn't really breastfeed in public quite often). But at home I just wear my sports bra and it was more comfortable for me. And since I didn't go out that often in the first few months, I only really needed one nursing bra. I got my nursing bra from La Vie En Rose and was the only one that fit well - my size pre-pregnancy was 36A, so most of the nursing bras were just too big for me.
7. Bath Tub - Some people use their sink, but I used our tub right away - it was just a regular baby bath tub that was just given to us. And when the boys were smaller, I would just hold them with one hand and use the other hand to bathe them. Since this was just given to us, I didn't really have any choice. But if I had to buy one, I'd probably get the collapsible ones (so that it doesn't take much space), but I can't really say much about it since we don't own one.
8. Baby Nail Clipper - Newborn baby's nails are SHARP!! so you'll eventually have to clip them.. I wouldn't say you need to buy this before they are born, but maybe shortly after.
9. Breastfeeding Pillow - For me, the twin breastfeeding pillow worked well and for singleton moms, the regular breastfeeding pillow. I used this in the hospital too.
10. Bibs - I am very particular with bibs, I don't like the ones with rough velcro because they are scratchy. But the other less-scratchy type of velcro doesn't work well either because after a few wash it just doesn't stick well - which is why I prefer the snap on button type like this. Oh, and it has to be machine washable and I have to be able to pop it in the dryer - I think this is my rule for ALL baby stuff.
I think that's it! I'll update this if I remember anything else that I needed when the boys were first born (they're now 11 months so it's a bit harder to remember!)
I hope this helps! :)