This is general advice for everyone, but if you say your a "shirt and jeans type person" your really selling yourself short.
Your clothes can be a great way to express who you are. Shirt and jeans is a blank canvas. Look at celebrities who dress in a way you admire, or on apps like Pinterest for ideas on how to paint your blank canvas.
I agree, and I wish I understood this before - "
your clothes can be a great way to express who you are".
Before, I just wore whatever, I didn't express my interests or personality out of fear of ridicule and being kicked further into being "uncool"/unpopular/low status. I now see that I really was selling myself short, and I shouldn't have done that, I should have been myself and mouthed off to the haters if there were any. Who knows, maybe it was all in my head and no one would have cared.
I also repressed myself to try to be "cool" for "the hot girls", and that didn't work either.
All I really expressed, though I didn't mean to, was that I didn't have any money, and didn't have a style or fashion sense - I wasn't "with it" enough to put together a distinct "look", which said something about my personality. Or, that I didn't have any interests or personality to express. Like WillPower said, your outer world expresses your inner world, and at the time my inner world was either pessimistic, undecided/vague/clueless, only had a few narrow interests - it was either a mess of discouragement and indecision, or it was just blank and empty. I just did what was required of me and went home, I didn't think I needed, wanted, or could do much else to do something with my own life or engage with the world.
Doing what I did - the bare minimum/no conscious effort - didn't work. I wasn't expressing anything except that I didn't know what I was doing, and hadn't chosen enough interests and personality traits.
Trying to copy the "cool kids" wouldn't have worked either because it would have been inauthentic, it would have been me trying to be something that I'm obviously not.
I needed to have found myself, my interests especially things I actually did myself, not just things I liked made by others, before I found my style, and then I could have been more comfortable in my own skin.