The more kids I've had, the more I've questioned what I've really "needed" (I'm due with #4 in March) - due to space and how much use it gets or doesn't, and of course monetary reasons!
I could not live without a baby carrier - check out www.heavenlyhold.com and/or www.frogmama.com -- they have great info and tutorials on carriers that are great for you and baby! You can also find gently used carriers on diaperswappers.com
Other basics that we use often are: carseat (obviously), pack 'n play, bassinet, bouncy seat, breastpump & accessories, bottles, clothes and diapers.
Everything else? We could definitely do without! Especially the infant bathtub, kickmats, monitors, and diaper champ. With my last 2 I didn't even use the Boppy, though I loved if for my first. If you feel like you really need or want these items or others, check out consignment shops -- you'll get great items for at least half of the price!
You'll most likely get a lot of blankets, clothes, books, and soft toys as gifts ~ these are a couple of things I'd avoid buying, unless you find a really great deal :)
Enjoy your newest addition!