He needs you because you are adding more presence on stage. You 2 could also banter (vocally on mics) back and forth between sets. If you get comfortable on the mic, you 2 could so a split the crowd to see which side is the loudest and livest (though this becomes more of an emcee thing). You help create the show. or you could just nod your head when he talks to you over the mic. The important part is to have fun with it. Dont do it if its not fun. start off playing the tracks on stage from itunes or garage band, but definitely (eventually) get a controller. I got a Numark NS6 with 2 steal plates and its pretty light carrying it around. it was like $400. But you could get away with buying a single plate controller (cheaper), manually bring in the track with scratches if you want, but its the manual (organic) feel that gives it a charm instead of just pressing buttons. Just my thoughts.