I’d suggest eBay. I started cleaning out my moms basement during COVID and have been getting about $500/ month. At first I was taking things to shops but then realized I could just download the app, take a photo of the stuff with my phone and upload it to eBay. Oddly enough, the same guy at GameStop or wherever who will offer you $1.50 for your game will probably be scrolling eBay paying three times that for the same game. Also with the ap they fill out most of the post for you based on similar items and you can print shipping labels at a discount. Only inconvenience is having to go to the post office a couple times a week (though at least you don’t have to wait in line) and making an initial investment in packing tape, boxes, etc. (though it is also a helpful way to recycle old shipping materials).