Twin mum here and mum of 5:
Dealing with the practicalities first
Pram: think about where you live, types of roads/pavements etc, measure your doorways and front door, and think of places you will be going regularly with the pram like doctors surgery etc. I had 2 prams the Silvercross Wave Twin - it’s a tandem so the same width and a single pram as the babies are stacked rather than side by side. Brilliant pram when in the car seat and carrycot stage and was great for getting through the narrow doors in the village I live in, though once we moved to the seat stage it was difficult to handle and heavy so I got a second hand baby jogger city mini, cost me £25 of marketplace and I use it daily for the school run, it’s not pretty but it fits through my doors and the twins like to sit side by side.
Sleep: you’ll want plenty of safe sleep spaces especially in the early days. I recommend buying 2 cots, put one downstairs and one upstairs, twins can share both for around the first 6 months. Once the upstairs cot is too snug to share, move the second cot upstairs. I wish I had done this myself as would have saved time and money. I had 2 Moses baskets, 2 bedside cribs and then 2 cots, it was not necessary I could have just made do with just the 2 cots from the start.
Play: You will want 2 bouncy chairs: try to get ones that will last beyond 6 months. I got infant to toddler rocker chairs and mine used theirs until they were 2. Playpen: once they start crawling get the biggest one your living room will accommodate, it’s somewhere safe to put them both while you nip to the loo or make a brew and is essential for a bit of sanity saving.
Feeding: I recommend the Milton Cold sterilising system, so much easier to deal with and less faff than a steam steriliser as you can just add to it as needed throughout the day and change the water once every 24hours.
You will need many many bottles at least 6 for each baby.
I have seen people recommend the twin feeding pillow which is great but consider also getting 2 single ones, that way your DD can sit and feed one baby, and you or someone else can feed the other.
Muslin squares: just go ahead and buy those in bulk!!!
Clothing: as many have said I wouldn’t bother with outfits just lots of comfy sleepsuits and vests. Get on Vinted and Facebook where there are lots of specific twin sellers and you can buy a bundle.
You can get everything you need second hand, car seats and mattresses were the only big things I bought brand new.