wheelset and cranks
get a decent wheelset maybe iro or go all out and get phils on open pros - (I did)
crankset and bb - sugino rd2 messenger on a budget or miche primato pista
pedals - mks sylvan kit with clips and straps or a set of decent spds and some
mountain shoes
cog - eai soma anything but the cheap da 1/8" and a decent lockring too
chain - 1/8" kmc
you can do all of this for around 3 or four hundred ish I would do it incrimentally though like most of us do