What tights/makeup am I supposed to get for a musical? (I'm a guy)

It might be a bit awkward if they’re high heels.
You can find tights anywhere, like pantyhose and such, and if you get a large size they should be able to fit. If you specifically need dance tights then you should check out your local dance store and someone will be able to help you find a good fit.

As far as guys and stage makeup they usually just wear the bare minimum. That usually means: eyeliner, mascara, blush, and maybe the slightest hint of lipstick and eyeshadow (but make sure it’s a more neutral color). The blush and eyeliner are the most important.

If you have a sister you should be able to borrow all of those things from her.
The makeup is to give you a little bit of color so you don’t look like a ghost under the stage lights, and it’s easier to see your face if it’s exaggerated with makeup.

If the shoes fit where them. Eyeliner and foundation are all I use when on stage otherwise I would ask as to the specifics of what your drama teacher wants. As for tights I’m with @squidcake go the local dance shop.