Dillard's in the BCBG section. Then my "source" said Waco doesn't have a good selection so she frequently got dresses in Dallas.
There is a store in the Grapevine Mills Mall....you enter at Rainforest Cafe entrance and turn right...it is dead end I believe with that walkway. Anyway, it has specialty dresses, bridals etc at drastically reduced prices. We have been there several times as well as the Dillard's here and in Temple.
Honestly, we just made it a habit of looking and bought when we found sales...several dresses at a time once or twice.
Also, if you have a son...the first time he needs a tux, buy one from the JCPenney Catalogue. They are $99 right after New Years and you cannot rent one for that. Also, there is an Al's Formals outlet in Houston where they sell previously rented tux. We bought son his bow tie, vest and wing collar shirt there and the total was $30.