I would advise not to stay on the backbay( Imperial palace, palace, or boomtown).
Both times I have been to biloxi I stayed at the Isle of Capri, which is in walking distance from Casino magic and the Grand. I believe any of these three give you the best area.

The President and Treasure Bay are farther west on beach blvd towards Gulfport.

The Gulfport casinos (Copa and Grand) are maybe 10 miles farther up beach blvd.

If looking for best Price I would try the Imperial Palace.When we were last in there the employees out numbered the gamblers about 3to1, but that was early april.

That sould give you the Idea of the set up in biloxi. I get my information from American Casino Guild, I wouldn't plan a trip without it