Seoul City Tour - Which district is good?

Hello friends! I'm Naran from Mongolia. I'm planning to get a brightening treatment in Seoul this fall. I'm very interested in Gangnam and Apgujeong, but I'm not sure where the best place to stay is. I'm curious about which neighborhoods are good right now, if it's cold to stay there, or if there are other neighborhoods.

Also, where do other international friends usually stay? Are all-inclusive shops in one place, or are they spread out nearby? Since this is my first time in Seoul, I don't understand the map very well. If you have experience traveling here, I'd like to ask which neighborhoods were good and where you stayed. Feel free to ask any questions, no matter how silly or difficult they may seem!