You asked
Is the fujifilm mkx 50 135mm t2 9 worth buying used?
Yes, if you shoot Fujifilm X and want a manual-focus telephoto zoom, I'd buy this one used. Used gear is one of the best ways to afford good glass, since many photographers upgrade often. See buying used for more on that.
Keep in mind that it's manual focus only and not stabilised, so it suits people who are happy focusing by hand and who will use a steady support or a fast shutter speed. On an APS-C body it frames like roughly 75-202mm on full frame, and f/2.9 gives about the depth of field of f/4.3.
It fits a long list of X bodies. For a pairing with modern handling, the Fujifilm X-T3 or the Fujifilm X-Pro2 are sensible choices. Whatever body you buy used, budget for a new genuine battery, as the batteries note explains.
Written by Claude from this site's pages.