My favorite brand? Any and everything from the Disney Store - even some that have issues will go for big bucks.
As I always say - be on the lookout for less popular characters from movies as well. Maybe your daughter LOVES Beauty and the Beast and wants the whole family to set out with her as Belle, Dad as the Beast, Mom as Mrs. Pots and baby brother as Lumiere or Cogsworth? Well to do this by shopping on eBay it will cost your family at least $300 if not more. Yep. Really.
So definitely pick up those popular characters but the real cash is in the adult costumes and the lesser known characters. For example - Emperor Zurg from Toy Story - they are going for $70-$90 right now and I'm kicking myself because I passed one up last fall!
I also re-sell my own kids costumes the year after they wear them. Remember my post from last Halloween with the adorable Nemo & Dorothy of Oz? Check it out HERE!
I bought Nemo off Craigslist for $10 last summer sometime, and my little cutie wore it 3 times over Halloween! Usually its just the once for Trick or Treating but we had a couple of different costume events and parties last year. I stored it for the next 11 months and then it sold within 1 day of listing for $49.99! Now another cutie will get to be super adorable this year and I'll use the profit toward more costumes! Now that is what I call getting your money's worth!
This Disney Store Lilo costume sold within 2 days for $39.99 + shipping to Isreal. It even had some of the tulle ripping off in a couple of places which was fully disclosed in the listing and off it went. Fingers crossed it makes it over seas safely! Oh did I mention I bought this on clearance at the consignment store last year after Halloween and my daughter used it for dress ups and play dates over and over as well?! Gotta love it!
I have a couple more costumes listed up currently and you better believe I'll be sourcing for them this weekend. I am not exclusive to the Disney Store either. Some other brands that do well are: Gap, Gymboree, Pottery Barn Kids, Babystyle and lots more! I recommend doing some research before you buy just to see what's going for the big bucks and what may be worth leaving behind. For example: I typed in Disney Store Costume into the search and sorted by highest price and completed listings. You can do the same for Pottery Barn Costume etc.