What a baby needs isn't the same thing as what a baby needs.
You don't need as much as they try to sell you. Rockers, toys, so many bottles, hats, etc. Just get 1 rocker. More money doesn't mean better. Buy used. Try to find a Facebook buy/sell/trade board. Moms love selling old baby gear on there for a fraction of retail. You don't need a high chair for 4 months. You'll be ditching stuff every few months. Save the money for babysitters. Get on a diaper subscription from either Amazon or Diapers.com.
Try to be there for all the prenatal appointments. Rub her pregnant feet. Bring her water to help her stay hydrated.
When she gives birth, be the information liaison. People will be texting and calling. You handle that. Schedule visitors at the hospital, but leave lots of time for sleeping and rest. Oh and be prepared with food and snacks for yourself. The hospital only feeds patients, which you are not lol. Bring your own pillow and a blanket.
As a dad, be ready to take initiative on things like diaper changes, giving the baby baths, cleaning the house, cooking (or bringing food, however you get it), laundry. She will be exhausted and breastfeeding a baby round the clock. You can help by bringing the baby to her when it's time to nurse and letting mom sleep. Bring get snacks and water when she's feeding the baby. Sometimes cluster feeding pins a breastfeeding mom down for hours.
Sometimes babies mix up night and day. If that happens, try to let mom sleep in between feeds add much as possible, since she will be awake with baby at night. Make sure you and mom are getting 6 hrs of unbroken sleep every 2 days at minimum. Sleep deprivation plus baby blues can make things harder as her emotions will be all over the place. Your relationship will be tested the first 6 weeks. You'll both be exhausted, she probably will not be cleared for sex yet, and she'll be hormonal.
Take pictures. She won't feel pretty right after birth and maybe even for a few months more, but this is your guys' story and you'll wish you had documented more. Take pics during the pregnancy, too.
Read up about car seat safety and installation. Car seats for the Littles is a good resource. Annoying name, but they are super helpful.
Toddler just woke from her nap, so maybe someone else can add more.
It isn't uncommon for new parents to give out $400-500 worth of newborn stuff, another couple hundred of 0-3, 3-6, etc. Crib, cradle, bassinet, side sleeper, and rocker. All we use is the bassinet and rocker and I know we'll use the crib later, but wow.
I wish we had returned every single piece of clothing because it's all generic made-in-China trash with all the dumb "handsome" or "mommy's little boy/girl" or "I love daddy". I know my newborn is a bitter malcontent whose soul was forged in agony and hatred, and he already has a bald spot so every piece of clothing he has is satirical at best.'