I would maybe somehow add a lil color to the all black look... maybe a belt or a ribbon in your hair... Just something to offset the alll black look......... And if at all possible, a different colored top..... Hey your 15, so dress like a 15 year old... Wear something that is comfortable and you feel good in... We always do better when we feel comfy in what we have on....Maybe you could ask your mom before you interview if what you have on looks good.. Moms most of the time give good advice...... . Good luck........ Hope you get a job for the summer............