Almost everything - buy it used. Better yet, "put the word out" among friends, relatives and co-workers that you are happy to take/borrow leftover baby items. Clothes, books, toys, baby carrier/sling, stroller, et cetera. Big items we got for free are a Pack-n-play, Nice stroller, very nice handmade wooden toy chest, powered swing (loaner).
Your kid is going to be eating floor food, bugs, boogers, leaves and dirt. And that's a good thing. They need to build up a healthy set of microflora. Don't start freaking out about used clothes. Or cloth diapers.
For some items there are potential safety concerns: Car seat. Supposed to be thrown out in less than 6 years, no accidents. Crib. Make sure the slats/bars meet modern spacing standards (simple test - if you can fit a Coke can between the slats, they are too wide.) High chair. Get one with a good buckle/strap so that the baby won't climb/slide out. We ended up spending like $20 for an 'Antelop' high chair at Ikea. It's tough enough they are the standard high chair in the cafe with constant use.
Did we buy other stuff? Sure. But not much, between baby shower and freebies. Most clothes have been free from Kohl's - for some reason, about once a month they send me a $10 gift card. I walk over at lunch, get 2-3 baby clothing items from the clearance area, never spend more than $1 each - which is cheaper than used.
We have been buying new shoes, as there are too many crap shoes out there with stiff soles. We get the cheap "Skidders" - Target, or most recently Big Lot's. Something like $12/pair at Target, $5 at Big Lot's. Easy slip-on, flexible soles. Just enough shoe to keep feet from getting cut up/filthy/whatever. He only wears them outside, when we leave our yard.