I prefer resale shops.  You can find them all over Busan and double so near any college campus.  Cheap prices, good people (usually) and delivery included (usually).

I bought most of what didnt come with my apartment at a store a few blocks away.  Dresser, Bookshelves, and a table for under 100,000W.

Just look for a store with a bunch of furniture sitting outside the door and wander in to see what they have.