I think it's a good idea to define your problem before spending money on a solution. Sets of files (anything?) may seem attractive, and may appear to save a little money, but will you end up with several things in the set which never get used? With files, I think you need a range of cuts at least as much as a range of shapes, and the sets of needle files that I've seen have been of one cut only. I have bought my needle files individually, as needed, and am particularly glad to have been able to get No 6 cut Vallorbe files here in NZ, where it's often difficult to get things that aren't of indifferent quality. And, as others have suggested, you need to keep separate files for ferrous and non-ferrous application. As usual, buy cheap, pay twice…