If its outside and hot, I'd wear some tight and sexy short jeans shorts and a bikini top
Sexy jeans and a sparkly corton top. Dont forget your cozy cotton sweatshirt.
Since its outdoors you need to be very conscious of the time the concert starts (and approximately when it ends). It never hurts to check the weather for that day and time of the concert. The best thing to do is wear something comfortable (you definitely don't want to be too hot or too cold). You might want to try some distressed jeans with a nice tank top and some converse, high waist jeans/denim shorts with a cute crop top or a tank top and some converse are nice too.
A nice skirt or colored jeans shorts. A sparkly shirt. Do something like curl or straighten your hair.
I'm going to see Fall Out Boy and Paramore, too (my concert is on the eleventh!) If it'll be warm out, I'd wear shorts with a top. Or you could wear jeans. Or a skirt (but make sure you wear boy shorts or something underneath). The most important thing is that you wear close-toed shoes! You do not want to be in flip flops at a concert.
Skinny jeans, your nicest shoes, and your best tank/sequined shirt. It will be much hotter than you think, but cold at first, so wear a cami or tank or strapless top, but wear a cardi or shrug at the beginning.
