i've played with some solid pro's (68-71 average) who still use only starter clubs. i bought a whole set cuz i made it to pro in 2 days and i thought the new clubs would continue cutting strokes off my score.
the new clubs perform better than the starters. HOWEVER, they are harder to hit perfect as consistently. they take some getting used to... and some experimenting with new balls. it is generally recommended to start with a driver and a putter.. i particular like the Z-wedges and would recommend one of those as well. once you get used to them... you'll gain distance off the tee, more accuracy putting, and the ability to stick shots right next to the whole from the first cut of rough with the Z wedge.