I shop carefully and look for bargains and I’ve actually been pretty happy with most of my things.
As new second hand Passier Optimum, bought over a decade ago, still great for me and mare. I had D rings put on the back for latigo strings and go on big trail rides in it. Ogilvy dressage baby pads for that saddle, Lemieux CC for my jump saddle. I just have a couple of each in our best colors, and it stops me from collecting random pads! Also finally got a mohair string endurance girth for the dressage saddle and that has made mare much happier, no rubs at all. Having gear that all fits together is priceless 
My disappointments have been minor and usually about lower cost items. I started out as re-rider buying Greenhawks comfortable and affordable house brand breeches, but I wore through the actual fake suede full seats in a year! On multiple pairs! I upgraded to Pikeur and Cavallo I found on discount, and while they are fading, they are still going strong years later. Same with the low cost SSG grip or fleece gloves from Greenhawk. They split really fast. I upgraded to “glove liners” for skiing which have silicon palms and fleece inside and are similar lightweight to riding gloves, and they have been in use for years now.