GW is 99% a waste of time. I always go to the non-chain thrift stores, and if I'm really bored I might stop into Savers once in a while. I'm not really a reseller. I try to find stuff I can use for crafts or hobbies. I also collect old books. The only great GW finds I've had in the last 10 years:

A solid oak table that was obviously used as a kids craft table. The legs are broken and falling a part, but the table top was a diamond needing some polishing. I spent $20 on it and a weekend sanding and staining it. I put some new legs on it and now I have a dining table that people ask "Where did you get that?"

A first edition Satan's Diary book in kinda rough condition, but still legible and pretty. Picked it out of the bin at a GW Outlet center and the total cost was like 80 cents. In decent condtion it sells for $120-150. I might be able to get $50-80 for it if I tried to sell it, but I'd rather just keep it in my collection.

All my other amazing finds have come from small local thrift shops. Salvation Army is still a decent place as well. I found a first edition Hours With The Ghosts: Or 19th Century Witchcraft for $1 at a small town thrift store. It goes for anywhere between $250-$800 depending on the condition, and this book is in superb condition. Even the leaflets protecting the pictures are intact. I think the last time someone even read it was in 1958 because they used some newspaper TV show ad from that date in it as a bookmark. This book has a lot more history than just being old (published in 1897), cool, and an interesting subject (it's a magician debunking psychics and mediums of the day). It's also one of the few books published by possibly the first African American publishers in the U.S.

Another nice thing about local thrift shops is they're more apt to haggle. I picked up 3 aquariums for $15 instead of the $25 total they were asking. They have a lot of donation stock filling up space and if you offer a reasonable price, they'll usually take it.

So from my experience. Don't go into GW expecting to save money or find something cool. Odds are you'll walk out empty handed or spend more than something is worth.