Before buying or making anything, trot out the loaners and hand-me-downs. The expectant parents need lots of everything and will be eternally grateful.
Clothes Yes, twins need twice as much clothing, but don't make any assumptions about how these babies will be dressed. My fraternal twin daughters look nothing alike and have no more in common genetically than sequentially born siblings, so I don't dress them the same. Look for versatile items that are easy to mix, match, layer and launder, like American Apparel onesies and BabyLegs. That said, there are some incredible garments that are fun for multiples, like the onesies pictured above from Etsy seller Oliver Blu Designs, perfect for our dachshund loving family.
Feeding Mealtime can feel like a military operation, and what works for one baby doesn't always work for a small posse. Devices like the Beaba Babycook aren't practical for turning out large quantities of food. Expectant parents who don't have a fully equipped kitchen but intend to make their babies' food from scratch would benefit tremendously from a steamer and a Cuisinart or immersion blender. For bottle feeding many parents of multiples swear by Podees.
Toys & Books No matter what, parents expecting multiples are anxious that their home will be overrun by baby toys, so the best choices for multiples come in small packages. There are a few personal toys that we have in duplicate (Sophie the Giraffe and the Squish), but in general we like toys that the girls can take turns with or enjoy together, like an activity cube. Sets of small board books like the Bright Baby Chunky Book Tray are great because there are enough to go around and they are easily stowed in an overstuffed diaper bag.
Gear This is extremely subjective, so when in doubt, ask. We are a two Ergo, two Gymini family who never uses more than one bouncy seat or pack and play at a time. We had no interest in new or matching; with our family's expanding carbon footprint we were grateful to borrow briefly used space-hogs like swings and exersaucers. Of course, some things are non-negotiable, so consider chipping in with friends on some of the costliest necessities like car seats and strollers; those requisite items make it possible for new parents to get out of the house with the babies. Those things are a family''s freedom and mobility.
Remember that love don't cost a thing. If all new parents are thankful for a home-cooked meal, a hand around the house or a few hours to themselves, then parents of multiples will appreciate that support exponentially.