Oily skin over-cleanses. That is most of the problem. Strip the face twice a day with a squeaky foaming cleanser and the sebum comes back harder by lunchtime, which reads as proof that the skin is oily and produces more scrubbing.
Morning. Lukewarm water, or a low-pH gel cleanser if you sweat overnight. ₩10,000–₩15,000 buys a decent one and the shelf is full of them. Then Torriden Dive-In Low Molecular Hyaluronic Acid Serum, 50ml, ₩15,000–₩22,000, which is hydration with no oil in it at all. Finish with Beauty of Joseon Relief Sun, SPF50+ PA++++, 50ml, ₩12,000–₩18,000. It dries matte, which oily skin tends to read as a feature.
Night. Cleansing oil or balm first if you wore sunscreen, which you did, then the gel cleanser. Anua Heartleaf 77% Soothing Toner, 250ml, ₩18,000–₩25,000, pressed in with damp hands rather than a cotton pad. Torriden serum again. Cream only if the skin feels tight ten minutes later. Through a Seoul August, plenty of people skip it entirely.
Two or three nights a week, SKINFOOD Carrot Carotene Calming Water Pads, 60 pads for ₩18,000–₩25,000, can replace the toner step. Three separate Olive Young staff picked them in the tally, which is a strong signal for something this cheap.
The downsides, honestly. The Torriden serum is hydration and nothing else, and left bare in dry air the water evaporates off your face. The Anua toner is very light and will not carry dry patches through a cold winter on its own. The carrot pads are single-use, so you are buying packaging waste, and the tub is heavy enough to be a checked-bag item. Relief Sun uses chemical filters that sting some people's eyes on a hot day.
For oil and uneven tone at the same time, niacinamide is the ingredient worth testing. The Ordinary Niacinamide 10% + Zinc 1% is ₩10,000–₩16,000 for 30ml, the cheapest way to find out whether your skin likes it. I stopped repurchasing it after the second bottle because 10% stung along my nose every time. 2–5% is the sensible starting strength, and a bigger number on the label is not a better product. The breakouts and pores page has the rest of it, including hydrocolloid spot patches, which are the one genuinely Korean invention in this category.
Sunscreen is its own rabbit hole. Start with the sunscreen page or the no-white-cast comparison, and reapply every two to three hours outdoors. The SPF number on the box assumes far more product than anyone actually applies.