This might be a stretch, but the jacket I’ve been wearing this week is second-hand, and most of my gear was purchased second-hand or traded for.
It’s a red Patagonia tech fleece, discovered on eBay for a hefty discount because it has white paint splatters on it. I was able to use rubbing alcohol to remove much of the paint, and the splatters that remain give it character. 
I believe there is already so much gear and clothing in circulation. Buying fewer items and/or gear that is secondhand lessens the demand for petroleum-sourced plastics on the front end, and landfill space on the back end.
In the past I have also done a few Tuesdays for Trash runs, collecting neighborhood trash into a plastic bag along my route. Given the frequency with which people like to toss their coffee cups, I should probably do another, though sometimes it’s difficult to stay positive when you pick up all the trash and a week later it’s all back again.
