I use Vinted for stuff that I think is in good condition and will sell quickly. I found that if you upload a lot of stuff at a time it tends to go quite quickly, so you are not back and forth to the post office all the time, you can do them in big batches. The app and website are both really easy to use. Some users also do swaps and you can use the money you make to buy stuff from other users.
For stuff I am not sure about, I have used an app called reGain. You box everything up and send it to them. They sort out stuff for charity shops (British red cross I think) and then recycle the rest. In return you get a discount code to use for various online stores. I really liked using it as I knew the clothes wouldn't just go to landfill and I used the discounts to buy stuff for my children so I wasn't just shopping for the sake of shopping
For stuff I am not sure about, I have used an app called reGain. You box everything up and send it to them. They sort out stuff for charity shops (British red cross I think) and then recycle the rest. In return you get a discount code to use for various online stores. I really liked using it as I knew the clothes wouldn't just go to landfill and I used the discounts to buy stuff for my children so I wasn't just shopping for the sake of shopping