That's so awesome!! And congrats on getting the opportunity
I've always wanted to work at a fashion magazine
I would say that depending on the magazine and the atmosphere, you have different options. I know a lot of magazine's allow there employees to wear jeans, and if you're up for it you could wear a really cute pair of fitted jeans with a cute tweed jacket. Or maybe for a more conservative outfit you can wear a simple suit, and then wear a fun, bright color, trendy top underneath. Hope this helps a bit. Keep us posted, cuz I can't wait to hear how it goes.