I'm going to be devil's advocate here and add a counter-voice to all the stuff mentioned thus far in this thread. To the OP, if you're feeling anxiety and stress because of pressure to wear nice clothes, then you should absolutely prioritise wearing what you want; there's no point in being there if it's going to add so much stress. As many people have mentioned thus far as well, nobody is going to consciously disrespect you, except for really judgmental people (who you're better off not dealing with anyway). I just want to make it broadly clear that I absolutely agree with the points many have raised thus far.
Here's the catch; even though most people are nice, there are *some* judgmental people out there. Unfortunately, many of these kinds of people are also likely to be the kinds who have power in certain parts of campus - think presidents of certain societies, career hacks, people trying to climb the corporate ladder, etc. I understand this is a generalisation (I know plenty of people like that who are as sweet and fair as you can get), but equally it's fairly intuitive that people with an obsession for power/wealth are probably also somewhat superficial. If you want to impress these kinds of people, sometimes there is a basic standard of what you have to wear to do so. Now, the good thing here is that you probably don't need to care about them; in fact, unless you're a career hack or something yourself, it likely doesn't matter. But I just wanted to raise the idea that sometimes, it *does* make a difference what you wear, and that we shouldn't totally disregard such circumstances. Also, I do think at uni people tend to sometimes be a bit more judgy in terms of "hooking up" with regards to superficial things about appearance - but that's again probably fairly intuitive, since casual hook-ups are just done with people you find hot (ie. have no deeper meaning); again, if you don't want any part in that, don't worry about it (and relationships are way different from hook-ups! People care more about your personality there, not how you dress).
In summary - to the OP specifically - believe in yourself, and know that it is absolutely okay to dress however you want, and trust in human decency that nobody will care, and that if you are a good person, and try hard (as Slothpomba pointed out), they will love you, given time. But also, don't *completely* dismiss the significance of what you wear, because in some very particular circumstances, it can be important too (though you can just as easily opt-out of those circumstances; in which case, again, do whatever you want!!!)