There’s a secondhand store online, called Like Twice, that sells gently used nice clothing for women. It is one of the better ones I’ve seen because they are VERY clear about what they will and will not accept.
I’ve been to secondhand stores locally, and sometimes been successful selling items back, but sometimes it’s a puzzle what criteria they use to take things back in and what they calculate as what it is worth. This site is really easy.
When you join through this link, you will be credited $10 to spend. You can also sell items back to them if they meet the criteria. It’s for women’s clothes, not children or men’s, so those you should still stick to some of the local places.