This place was a madhouse on Halloween weekend, but I found exactly what I needed and was able to get through the line in under five minutes so I suppose I can't really complain! I was on the hunt for an olive green army-esque shirt for my Joyce Byers (Stranger Things) costume and I was able to snag one for $7 - a much better deal than the slightly too small new one I got at Target the day before.
Clothes are separated by type (skirts, long-sleeved blouses, etc.) and then by size. The racks are crazy long, so if you are on the wrong side for your size you've got to go what feels like halfway through the store to be able to make your way down the other side of the rack. Signs are small so sometimes you miss what you're looking for.
The store is kind of dingy and the inside reminds me of my 80s childhood, but I admit you're not going to Savers for the ambiance.
As for their Halloween selection, for years I've driven past their "We've Got Halloween Costumes" sign and assumed that like Goodwill they've assembled a few racks of used costumes and more out-there pieces of clothing. I was wrong. They've got about six good-sized racks with new costumes (most around $25) and, of more interest to me, cheap accessories and wigs. They had a ton of wig styles, each for about $8. Definitely keeping that in mind for the future.
Obvious tip: go on an off time if Halloween goodies are what you're looking for.