In addition to Mills, I suggest Karen Ho's ethnographic research on Wall Street. This could be a good start. https://books.google.kg/books?hl=en&lr=&id=UbQFDAAAQBAJ&oi=fnd&pg=PA29&dq=karen+ho+studying+up&ots=fN1lUto95M&sig=cm4Wjq9Dp5v0isQK1W-SwoT8pW8&redir_esc=y#v=onepage&q=karen%20ho%20studying%20up&f=false
Another starting point should be the volume edited by François Denord, Mikael Palme and Bertrand Reau; "Researching elites and power: Theory, methods, analyses"