The last time I went to a concert was when I was much younger and had no sense of style. I'm going to an indie/alternative rock concert next month at the House of Blues. The weather ought to be pretty warm around then. I'm not sure what kind of attire is appropriate.
A lot of people, girls N guys, wil wear jeans N a rock tee shirt. Often when I went to concerts, girls that wore a fancier top would buy a concert tee N either pull it over their current top or change in the ladie's room. Really, anything you like to wear is appropriate, but you might want to make sure it's comfy N non-restricting, because people do a lot of moving around N waving their fists int he air, (LOL) or ESPECIALLY if you feel like getting in a mosh pit. If you don't, you can still enjoy the show N avoid moshing all together. Have fun...
No matter what you wear, be sure to put a rounded red dot on your forehead between your eyes or just a little up. and put your hands together like your praying and shake your hips! INDIE INDIE INDIE bollywood!...LOL:))
Personally I just wear basically what I would wear on an everyday basis. I don't really know what your personal style is, but wearing skinny jeans, a pair of sneakers or boots like Doc Martens (ultimate concert shoes, no one can step on your feet, haha), and a cute casual shirt is always good. Just don't wear the shirt of the band you're seeing, haha. I'd wear one that is kind of loose, because it's more comfortable and you won't get overheated. Tank tops are especially great if it's warm enough.
Keep it simple cause you'll be jumping around a lot and stuff, but if you want to sort of jazz up your outfit a little, add some rings or small earrings. I tend to avoid necklaces cause I don't like the way they jangle when I move around.
But basically, wear what you like and don't overthink it. :)
rock tee/long over-sized shirt,skinny jeans,cropped jacket-if needed,long necklaces-with big...stuff-at-end-of-necklace -.-'' if you're gonna sit/just stand,small-stuff if you're gonna be jumping,all-stars if you're gonna sit,if you're gonna stand wear cheap shoes,they tend to get lost on concerts