What is the order of importance of the parts of an analogue rig?

Let's make it simple and categorize it into 4 groups: cartridge, tonearm, phono stage, and turntable (include platter, plinth, motor, bearing, mat, etc., into 1). This happens to be my thinking, but I am open minded to other opinions.

This is assuming you have a well matched set up across the board. Where can you get the most improvement from a change in one category?