Definitely recommend YesStyle for inspiration & subtle pieces, but do note that there's been some questionable debate on consumer ethics. That aside, I do agree that stuff there is a hit or a miss. Definitely check reviews before buying!! Some of my personal rule of thumbs when shopping there are:
1) Know what fabric you prefer best. I stay away from polyester and chiffon on a regular basis, but I've found some pieces on YesStyle that were too cute to pass up on. Ended up returning them all because they felt really cheap. (I have found some staple pieces for my wardrobe, though, so it's not entirely out of the question haha. Purchased this really soft mock-turtleneck sweater that I always get compliments on, for only ~$10!! No piling, even after 2-3 years. My former boss even loved it as well, and she asked me to purchase some for her too.)
2) Sizing is a SERIOUS issue. Yesstyle goes by Asian sizing so go for a size up if you're not petite or don't have a typical Asian physique. (I'm a size 00 and 5'0 for reference but there's been times where even their smallest sizes wouldn't fit me...)
3) They charge shipping fees for returns. I buy a lot of (Asian-branded) cosmetics from them which almost always works out for me but when it comes to clothing, anything that I'm unsure of goes in a separate order. That way, the return fee becomes easier to stomach. It's also only credit only. (OT, but I highly recommend 3CE/Stylenanda products! I prefer them over typical brands here in NA. Also, I know that I order often from them, so the credit only isn't an issue for me.)
Korean fashion emphasizes sleek/modern & minimalist style, almost always feminine yet appropriate office wear. A lot of dramas are sponsored, so clothing that you'll see on actors/actresses are likely from Korean brands. (IIRC, some actresses/actors prefer to wear their own clothing; that's why you'll sometimes see "poor" characters wearing high end stuff. I think Park Shin Hye has been caught a few times.)
In terms of casual fashion, I find that a lot of them mix lower brands with expensive statement pieces. (Bags, usually.) In terms of dressing oversized (such as in pictures above), you'll want to take notice of your body type and proportions as they tend to put a lot of thought into that. That's why even if one attempts to purchase the same ensemble as an actor/actress, it might not look the same. Most of the style above would look frumpy on me, unfortunately--but it's so nice to see on other people.
Trench coats and (oversized) blazers seem to be a must-have as well. (They also had (have?) a trend in the winter with oversized puffer jackets.) Most of the time, it's comfort + minimalism + neutral tones.
Personally, I like the Jung sister's fashion style, but it's not necessarily the same as above. They tend to emphasize their body in a subtle way more than hide it.
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Shout out to Kim Goeun's fashion in Cheese in the Trap, though! I'm pretty sure she's what made me buy my Alexander Wang Marti hahaha.
Try googling
minimalist Korean street style for some inspiration too.
so hearing some recommendations on Korean clothing brands would be great 
