Thank you so much for your reply. I really appreciate the way you went about answering me, but I've never had a job interview before so I would honestly still appreciate the first answer you could've given me. I seriously don't know what to say or how to act in a situation like this regardless of the job lol
Alright, happy to help with that, too!
As for what to wear for a coaching interview, it's less about how it makes you look than about how it makes you feel. You should feel comfortable, confident, and ready to coach. Wear something comfortable that you feel like you could coach in. And if you've got something that will make you feel more confident -- a lucky pair of shoes, a favorite t-shirt, a hairstyle you think looks great on you -- wear those! Again, it's not about how the clothes make you look, it's about how they make you feel. And if you find yourself stressing about it, then just throw on any random shirt and a pair of sweatpants and you're good to go. (One of the few luxuries this industry provides its workers is that we can pretty much go to work in PJs)
They'll likely ask about what sort of gymnastics background you have; that's easy, just answer honestly. You aced these questions before you even scheduled the interview.
They'll likely ask a few random other questions about school, or hobbies, or what your favorite time of the year is, or what kind of vegetable you'd be in a salad, or something else completely irrelevant to gymnastics coaching. The actual answers to these questions don't matter; what the interviewers are actually checking for with these questions is whether you're pleasant to talk to. Basically, don't swear at the interviewer, don't spend the entire interview avoiding eye contact, and don't bring up politics, and you'll do fine with these questions.
They'll ask what sorts of hours you're looking for; it's good to have an idea going in what hours you want to work. What days and times are you available? How many hours of coaching do you think you can do and still have the time and energy for school and family and friends and hobbies and other interests? (That second question is better to undershoot than to overshoot; it's easier to add more hours than it is to back off of hours you're already working)
Most importantly -- and perhaps most difficult -- is pay expectations. You should have an idea going in of what your goal is, and also what your minimum is. Being a new coach means you'll likely be on the lower end of the coaching payscale, but what that number should be varies widely depending on location and situation. I would at least find out what local fast food workers or grocery store checkout staff makes, and refuse to work for anything less than that (and honestly, I'd aim higher than that if you can). As a former gymnast, you already have experience, and that experience has significant value.