If you're expecting to find exactly what you want right away, this is not the place for you.
It is small and very crowded, most stuff is just piled up seemingly arbitrarily. Even the employees don't appear to know where things are.
I like to think of it as a scavenger hunt. If you have the time and patience, don't mind digging for things or crawling on a less than clean floor, there are gems to be found at great prices.