I didn't have twins, but 2 babies 20 months apart.
My must haves varied for each baby!
DS1: cotton stretchy blankets to snugly hold him down once wrapped (he was extremely wriggly), zip up (not stud) onesies because he pooed like crazy and I was forever changing in the night, lots of Muslin wraps as he weed/pooed/vomited sooo much!
DS2: dummies, he loved them! Muslin wraps. Baby bouncer. Sling. Rocking chair in front of television!!!