Two: Car seats double buggy moses baskets if you use them (we didn't, used to use the carry cots on the buggy instead). Cots - eventually but ours shared for five months in our room so its not an immediate need. Decent bouncy chair with support not just the little flimsy things. We had the infant to toddler rockers from fisher price and they were brilliant, could feed them in them. Bath supports
If you are FF have enough bottles to do all feeds in 24 hour period. I used to wash them all in one go so there was never any faffing around trying to clean / sterilise when you need them.
You cannot underestimate the amont of muslins you will need and try and stockpile some clothes - you don't want to have to be doing two loads of washing a day. Vests / sleepsuits. Anything else is a pain to change when they are tiny. IN the summer you'll probably just need short sleeved vests. Lightweight / jacket cardigan each for out and about.
Lots of cot sheets, say 6 cellular blankets. Two sleeping bags each if they are big enough to go into them.
One: Playmat / playgym things Jumperoo (although for later) Steriliser Monitor Babybath - if you can be bothered to use one - we did for a couple of weeks as the real bath has really deep sides that I couldn't lean over properly after csection.
I can't relaly think of anything else, ut I assure you will need less than you think! Things like top and tail bowls are not essential even though every list you will see tells you you need one!
I agree with the above, except I would say you can get away with one bath support early on. We only do baths when my husband is home, so we either each take one baby, or one person does the bath and the other does the drying and dressing. We'll get two seats when the babies are bigger and want to play in the bath together.
I you are thinking about giving breastfeeding a go, I couldn't have done it without my tandem feeding cushion. I had a harmony duo but there are other versions about too. Resale value was good, so not a complete waste of money of it doesn't work out. Also Lansinoh nipple cream (and start 'prepping' them before birth)