these are my own two cents, because club gigs are different than mobile gigs:
use mic as little as possible, people went there to dance and listen to music, not hear your pretty voice.
most clubs will want their disk jockeys to have the newest music, most singles come out in vynil first, some don't ever see the light of day on cd.
unless it's the strip club in the edge of town, it will probably have it's own system, and most likely they will be technics 1200s. (this may not apply for bars)
before you decide you want to go into the dj market, make sure you can dj first. Beatmixing is a MUST, scratching is a plus, and if all else fails, your music selection has to be top notch.
the mobile business is very different than the club business, please take this into consideration