Ok_Sand_'s journey

I received a call today asking me to come in tomorrow at a specific time, but the person on the other end didn't clarify if it was for an interview or something else. I agreed to show up, but now I'm second-guessing what I should wear since I didn't think to ask. I'm 17 and have been applying to over 40 jobs, so this is the first response I've gotten back. I have a pair of nice fitting black/grey jeans, several plain t-shirts, a few dress shirts in black and maroon, and some black slacks. I'm torn between going casual or formal. Also, I have some face piercings and I'm wondering if I should hide them or just let them be and address it when I get there. I'm feeling a bit anxious about the whole situation and could use some advice on how to present myself.