Congratulations!
I would get in touch with your local breastfeeding support group before baby arrives. You can get an idea of what to expect, how to solve common problems, and you'll already have the contacts there for if you do encounter difficulties.
Also try and make contact with sling and cloth nappy libraries.
Obviously bf and cloth nappies are much more eco friendly than formula and disposables, but they're also great places to meet other like-minded parents. 12 years on I'm still friends with several of my eco-conscious baby group crowd.
Babies really don't need much, and they certainly don't need much at all that's brand new.
Feeding:
If breastfeeding, all you need is reusable breast pads and lansinoh cream (for sore nipples).
I didn't bother with nursing bras or tops. Just wear a loose top over a stretchy vest. Lift top up, vest and bra down. It's easy to not show too much boob this way too.
Travel:
Sling - I'd definitely recommend visiting a sling library as different ones suit different people, it's important to get it fitted correctly and be aware of safety rules.
Car seat if you drive. This should be brand new.
Consider whether you need a pram as well, not everyone does. I did. Should be easy to get second hand. Do you have a Freecycle or Facebook eco group? Otherwise marketplace, eBay, NCT sale, etc.
Sleep:
Consider whether you want a traditional cot, a co sleeper cot, or co sleep in your bed )obviously being mindful of the rules. Cota can easily be picked up second hand, as can bedding, although your mattress should be new.
Baby should be in your room for at least 6 months so there's absolutely no point decorating and furnishing a nursery. Many of us keep them in with us for far longer than 6 months so a nursery designed for a newborn would be impractical by then anyway.
Clothes:
For the first few months all you need is sleep suits, vests, socks, cardigans, hats, pram suit if using a pram in cold weather (in a sling, do not use a pram suit as they can overheat - use layers). All this is easy to find second hand.
Hygiene:
Cloth nappies
Cloth wipes
No need for toiletries - water only at first
Other:
Muslins
Nail scissors
Thermometer
Changing mat
From memory, I think that's all we had when ours were newborns.