My best buys are one but TWO pairs of Vass Budapester that fit like they were custom-made for me. Better still, they were a bargain and I just grin every time I wear them!
Also an awesome pair of subtly colored seersucker pants by Coat by Boglioli. They look like classic seersucker but with a tiny bit of stretch and great slim cut.
Plus several great sportscoats from various sellers that I would never have found, or afforded, shopping in the usual places.
Of course, I've also had my share of mis-steps, many involving Mabitex bargains. Until I learned they just don't work for my build.
Oh and those drop dead gorgeous suede loafers where I didn't pay attention to the AAA width marking.