Johnston Road in the vicinity of Wanchai MTR station (especially on the inland side of the road) is where you’ll find a concentration of discount clothing outlets. Forget about a leisurely browse, interspersed with trying on garments in a spacious cubicle. This is shopper-eat-shopper territory, where sizes are haphazardly collected and where you can barely see the garments for the inventory (or something like that).
Amazing items are squashed in between unimaginable ugliness; your quest is to find them. The one reliable fact is that the prices are low, low, low, which makes up for the lack of convenience.
My advice? If you see something good, buy it, even if it’s the wrong size. You’re guaranteed to find someone back home who will love you for bringing back a bargain.