Trevor Osborne's plans were picked over a rival scheme by Future 3000, a firm owned by local businessman Richard Carr.
The casino will be the main new-build feature of the pavilion, which was built in 1929. It will be built on the Bath Road North car park site adjacent to the theatre.
Piers Gough, partner at CZWG, said: "The major aim is to ensure the future of the theatre. But I also want the casino to look gorgeous, not like the tin sheds you usually get."
Other key elements of the Osborne plan include bars, hospitality rooms, a restaurant in the pavilion and an interactive educational and entertainment attraction called Metropolis.
I want the casino to look gorgeous, not like the tin sheds you usually get
CZWG partner Piers Gough
The area in front of the building will be pedestrianised, with fountains and open-air ice-skating in winter.
Osborne was picked by High Peak council and Derbyshire council in December 2003 to finance the project. The proposals include an 87-bedroom, high-quality hotel, a spa in natural baths and a centre illustrating the history of the Crescent and Buxton's spa origins.