I'm hesistant to suggest this because many have an "eww" factor, but I've been *shocked* by some of the stuff (brand new with tags - even in my unusual size) at Goodwill/Salvation Army.
I started going because my kids like to Cosplay and I wasn't going to special order or even special buy stuff for the massive amounts of costumes they dress in (they're tweens/teens - not little kids) and go to meetups, etc.
I had an aversion to buying clothes that someone else wore (slight OCD in our house), until I started finding some amazing things with the original tags on them. I know for a fact that they get Ross overstock because they had 15 identical dresses all with the original Ross tags still on them.
The trick is to go multiple times (and go to multiple stores if you can). They get new stock every single day and there are literally "bargain hunters" as well as people from those trendy "vintage shops" there Every Single Day.
I went to Nordstrom Rack, I went to Macy's, I went to Ross, Kohl's, looked on Amazon and could never find anything I liked that actually looked good ON me. At the Salvation Army, I found a $300 bridesmaids dress (missing the sash - which I replaced for $2.50 at the fabric store) with its original tag for $13. And it fit like it was made for me.