PA system, microphones, cables and stands for the vocalist(s). Amplifiers and cables for all electric instruments. FLIGHT CASES for all instruments, or at LEAST the sturdiest cases you can get. Some means of recording shows for later review and critique. A mixer (or mixer amp/powered mixer) may not be necessary, but can be helpful; have someone who's not onstage (i.e. an engineer or board op) with the band to work it. A van or truck to carry equipment to shows is a plus. Brand names and vintage of equipment may vary widely. Do sound checks on-site if at ALL possible, before a show.