i don't know how to build a capsule wardrobe

hi, im 17 and broke and don't have a lot of money to spend on clothes. right now i have a pair of gray nike sweatpants and a pair of plain black sweatpants that i bought in 7th grade, i also have a pair of white nike sweatpants that i bought two years ago, and i have two plain black long sleeved shirts and one plain black sweater, i also have two plain black t-shirt and three white t-shirts. I don't know where to start or anything i think it's time to buy some new clothes because my classmates are laughing at me and talking behind my back and calling me a charity case for not having clothes, i tried to make them think how i like not having to think about what i wear and how successful people wear the same outfit and that type of crap and it worked a little bit, but now im realizing i actually kind of need to buy clothes.i saved up and i have around 70€ to spend. i was thinking of buying something for the warm weather that will be coming soon. I don't like anything that draws attention i like plain colored clothes and my favorite color is black, and im not big on pants because I don't like the feeling of them on my skin. so if anyone has any advice, I'll appreciate it :)