I frequent Gwangjang Market a lot, and I like to introduce it to friends who have newly arrived to Seoul or to friends who just enjoy eating.
You can find reasonably-priced food here. Mostly the stalls consist of noodles, spicy rice cakes, blood sausages, and dumplings, but occasionally other things such as Korean ramen and red-bean filled pastries:
I chose to sit down for the first time at this stall and ordered the dumplings, blood sausages and pork feet. The total came out to ₩16,000.
I in particular liked the blood sausages and dumplings, but it seemed the noodles were also popular (and will be my order for the next time).
While I enjoyed the stall food, I urge everyone to try the mung bean pancakes though. They can be found in various stalls. They serve the pancakes whole or cut into pieces, and also can be put into a cup for carrying convenience. One pancake is ₩4,000.
Gwangjang Market is very foreigner-friendly and most stalls have a few signs in various languages. There are also tour guides (you can spot them in their completely red attire) around most busy corners. I highly recommend those who like to eat or explore to visit the place at least once while in Seoul.