Planning a beauty trip to Seoul! Please recommend some skincare products and experiences!

Hi, this is Rei! I'm going to Seoul next month and I'm super excited! As someone who's fallen into the K-beauty rabbit hole, I want to try out lots of things there. 😄

Right now, I'm thinking of browsing skincare lines in department stores and experiencing the wide variety of sheet masks. Do you have any recommendations? I'm especially interested in lines for sensitive skin. Also, I'd like to try a beauty treatment, but do you know of any areas that are beginner-friendly and easy to try?

I'd also like to know which areas of Seoul are vibrant for skincare, and I'd love to hear from people who have actually been there about how local cosmetics shops compare to those in Japan. I'm not sure about my budget, so any information on that would be greatly appreciated.