So. This is my question. How do I do that as a 21 year old female? I'm 5'7", 120 lbs (which means I'm about as skinny as it gets while still being curvy enough... I have that athletic chick body type)
your body type sounds very similar to mine, you also sound about as low-maintenance as me, so here's my formula for success:
-no accessories that I can't sleep in or don't have a practical use for. (what's jewelry?)
-tops ranging from basic to cool, mostly the former, in classic colors that I know that I will always like. Black, green, and red are good examples.
-a couple pairs of jeans that fit well that I will wear into oblivion to get my money's worth, some shorts too
-a skirt that I bought strictly for a job interview. I hate dressing up so I buy only as needed.
-cool kicks (if you have cool, comfortable shoes then you can wear anything with them and you can wear them all the time) no heels.
anything else you do beyond the most basic things most guys won't notice.
As for dressing for your specific body type, you probably don't have to worry about that too much if your body is considered normal by clothing manufacturers. I have broad shoulders relative to my hips and I'm busty for my bone structure so I have trouble finding tops that look ok. I wear lots of tank tops, and hoodies when it is colder. I also recently discovered that small men's t-shirts work well.
The most important thing I can tell you is that it's possible to build your wardrobe around logical principles, like every other part of your life. If you don't prioritize what's important to you and makes the most sense to you then you'll probably end up with some haphazard collection of clothes you wear, clothes you rarely wear, and clothes you never wear because you bought them to fit someone else's standard of what you should wear. Don't compromise who you are.