I used to live in little black blazers like this on, layering them on over everything.  I love how a basic blazer, a little skirt, and a lot of sparkle can add a bit of polish to a rock tee and grunge flannel.

{H&M blazer (old, similar from Forever 21); J. Crew skirt and shirt (old, similar from J. Crew); Forever 21 tank and tights; ℅ Just Fabulous Abbie booties; Lulu Frost necklace; Ray Ban sunglasses}