1) Tonearm/Turntable (equally important, should be well-matched so they work together2) Phonostage3) Cartridge (but must match tonearm effective mass, and the better the tip and coils, the better off you are)
In the end, all three or four of these things should be well-matched, and in the same category of quality, so one or more of the components aren't being bottle-necked by the better component[s].
In the end, all three or four of these things should be well-matched, and in the same category of quality, so one or more of the components aren't being bottle-necked by the better component[s].