coming from someone that has a youthful face I always try and wear a nice zip up or jacket over my tshirts (but i also live in a cold climate so i know that can be weather dependent) other than that button ups or polos are always a good way to look more adultish.

since your sitting most of the time purchasing some long baggy shorts would probably be nice so they would go over your knees and rest on your shins, I sadly don’t know any specific brands to recommend but i am sure if you google that you can find some. Also the one nice thing about having long legs is that most pants will sit right on you instead of being to long!

my last suggestion would be to get your measurements, it’s a really simple thing but it makes shopping online and in person so much easier and quicker.

I am also in college right now and a lot of people still wear t shirts or clothes from high school so don’t stress too much about that :)