How to plan your shopping trips
Firstly, you got to take note of the closing time of the shopping streets. For places like Dongdaemun which never closes (even on public holidays), leave it to the last slot of your itinerary for the day. Secondly, plan it such that you have time to revisit that place on the last day in case you forgot to buy something or would like to get more of something. Furthermore, you could have compared the prices at various shops before deciding where to buy your stuff. Thirdly, look at the subway maps and plan it such that you can cut down on transport cost. For example, Myeongdong is near Namsan Tower and Namdaemun.
Most people fly to Korea to buy their cosmetics. The kpop craze has generated much interest in the cosmetics that Korean celebrity uses (natural look). Product of top popularity there is of course their BB cream. So, I shall first start with cosmetics.
Myeongdong is definitely the place to satisfy all your cosmetic needs. You see replicas of stores like Etude House, Missha, Tony Moly, Hanskin, Skinfood, Face Shop and Nature Republic in almost every alley you turn into. There's Laneige too but there's only one outlet there. As for the other brands, you can try out Watson or other pharmaceutical stores. However, do note that only the official stores will hand out lots of freebies. In Korea, they don't call it "free gifts". They call it "service". So just say thank you when the salesperson tells you service.
It is very important for you to grab a free map at the tourist information centre before venturing out. The map lists out all the stores in Myeongdong and shows you how to walk to Namdaemun.
What cosmetics I bought
I did my research online before buying the cosmetics. I trust reviews rather than the soft sell from salesperson.
Personally, I have very sensitive skin. I chanced upon a brand known as BRTC that was said to have healing properties. It was used by plastic surgeon in Germany to help patients heal their wounds. True enough, I did not develop any sensitive reaction to this product and I think that it has good coverage on top of its oil control abilities. Nonetheless, it is very hard to look for this product. I combed the entire Myeongdong but to no avail. Watson has ran out of stock. I bought mine from W-store at Ewha (opposite Sinchon Korail station (not the subway station), the place where all the tour buses will unload their passengers).
I also tried Dreamy girls BB cream from Skin79 (the store is located just beside the Sinchon Korail station) and Dr Jart Silver Label Rejuvenating BB Cream. I bought Skin79 because it was selling at a really cheap price (1 for 1) however, I was disappointed with its coverage. Maybe it can be used as a sunscreen? As for Dr Jart+, I am quite impressed with its coverage, similar to BRTC. For more detailed writeups on BB creams, you can visit this website http://kimoko.livejournal.com/197110.html. Singapore's watson is selling Dr Jart+, BRTC as well as Skin79 but at a higher price and without any freebies.
Another product I bought which I thought was really cool was the Lacvert eyeliner (used by Kim Yuna). It has two ends, one liquid and one pencil. Before buying it, I tried it on my hand and gave it a rub, it doesn't smerge. I have used it over here in Singapore on a really hot day. I perspired so much but yet, the eyeliner remained intact.
Next up is mascara. I bought a VOV mascara. I heard from my friend in Korea that the nail polish is also quite reputable. Thus, I bought one bottle of it from Artbox at Myeongdong.
As for skin care, I bought a sleeping pack from Laneige (popular product) and a sunblock which has oil control properties. Previously I was using La Roche recommended by the dermatologist but I find it a little oily. The laneige sunblock gave my face a matte look even after several hours outdoor. So far, I did not develop any allergic reaction to it.
You can shop for clothes at Ewha, Hongdae, Namdaemun and Dongdaemun. My friend in Korea recommended Bupyeong and Express Bus Terminal for really cheap clothes (unfortunately we didn't have time to travel there). T-shirts w/o hoodie usually sells at 5,000won per piece. Most shops do not allow you to try on. You can try to bargain for a cheaper price if you buy more than one piece.
Popular korean brands would include Banc and Colonize. I haven't seen any Colonize store but there's definitely a Banc store at Ewha near the subway exit.
My sis wanted me to help her buy DBSK stuff. My experience is that Myeongdong is not a place to get these stuffs. I bought a poster there on the first day which was way overpriced. I saw similar stuff in Namdaemun selling at less than half the price in Myeongdong. Also, remember to check the quality of the prints (expecially for posters that come in 12 pieces per pack). The price guide for posters is around 8,000won for a pack of 12. On the last day, after knowing the prices at Namdaemun, I purposely went back to Myeongdong to ask for the price of a DBSK mug and that person (knowing that I am a foreigner) told me 8,000won. You can get it for 3,000won at Namdaemun.
As for official stuff, you can get it from SPAO, that is if your idol is a SME artiste (Super Junior, SNSD, Shinee, etc.. unfortunately no more DBSK).
If you are looking for Idol keychains, earrings and necklaces, you can try out those accessories stores at Ewha and Myeongdong. Earrings are sold at 2,000won for a pair and necklaces ranges from 5,000won to 10,000won. Belts are sold at 5,000won and keychains are normally sold at 1,000 to 2,000won.
You can get sunglasses and spectacles from roadside stores at Myeongdong. These glasses are sold at around 5,000 to 15,000 won. I am sure you can bargain a little if you buy more. The style is pretty cool.
Need to buy some souvenirs back for your friends? Looking at those steel utensils around Namdaemun? Lemme tell ya a secret. You can get these utensils from Daiso (Myeongdong) at 2,000won for two pairs. We checked the prices everywhere and Daiso offered the lowest. Another thing we love to get from Namdaemun would be seaweeds known as lavers. I bought one whole big pack at 10,000won but I strongly believe that you can bargain the price down to 8,000won.