With clothes, buy for 1.5 babies (if you see what I mean) – you’ll need more clothes than for one, but not double.

Mainly 2 cots and 2 car seats – toys, playmats etc you could probably do with just the one of each and rotate them. Having 2 rockers / bouncers or swings could be handy tho (although perhaps 2 different styles and they can take it in turns)

You could get away with one pram, there’s lots out there built for 2 kids/babies. You could fit 2 of them in a cot for a while. You’ll definitely need oodles and oodles of nappies, wipes lotions etc. 2 car seats. Don’t stress, you got plenty of time to work it out. Even if you buy one of something and you realise you’ll need 2, just go get another one

You will pretty much need double of everything for 2 babies. Except a pram. And you could maybe get away with them sharing a cot for a little while. I really can’t think of much else you won’t need to have double of

when buying clothes I would always buy an outfit for each at the same time so they would match together not be clashing.
Not knowing the sex I would just have a four of most basics (singlets, pairs of socks, bodysuits, jumpsuits, etc) in white or a unisex colour because then you can build on that with colour when you know what you are having.
Keep in mind you will get given things, most cases double
put things on layby if your not sure that way you can cancel anything that you don’t want as you decide but I case they are there

get all the basic baby stuff now- get your car seats, double stroller, bassinetts/cots, bassinettes/cot sheets, clothes, wipes, blankets, wraps, change tables/mats, nappy bag, bouncers, bottles, sterilizers, nappy creams, face washers, lotions, powders, bath soaps/wash & shampoo & a baby bath

get later- high chairs, toys etc

Wow, firstly congrats! I can’t even comprehend having to get two of everything. But I imagine you will need two bouncers or similar, two beds, loads and loads of nappies and wipes. I don’t think there is much you will need two of, just stock up on clothes, singlets, nappies and wipes….hopefully all your loved ones will help fill in the blanks.