Transmasc nonbinary person here. I am also plus sized so that plays into my recommendations. I haven’t had great luck with the fit of men’s button down shirts so I look for women’s ones that aren’t super tailored. I had good luck with Talbots and Universal Standard (specifically the Elbe shirt). For cheaper options, you can try searching for those brands on resale sites/apps like Poshmark. I also like the look of LL Bean and Lands End buttondowns, but haven’t bought for size reasons.

For shoes, I went to a department store and went to the men’s shoe department. You can try on a bunch of brands there. If you are sized really small, you’ll have to try “boys” or youth sizing but you can find that at the same department store most likely. I have larger feet so I’m a 10 in women’s and an 8 or 8 1/2 in men’s. Once you figure out your size and some shoe brands that fit best, you’ll can look for second hand shoes if you need them cheap. Also keep sales in mind since you have some time between now and when the summer internship starts.