Man, fashion analysis is fascinating. Heck, shoes alone are the best rule of thumb personality indicator there is.
It seems to me, now that I think about it, that irl me and my avatar are rather diametrically opposed.
Thanks to my Weird Damn Job and it's unpredictable hours (It's 1am. How soon can you be here?), I'm rarely more than two degrees away from clothes I can haul cable under a stage in, even at my flashiest or nicest. I'm practical, lazy and cheap. Also, when you're under 5' tall, the clothing options get a little limited. I only ever wear pants (you can't climb fun things in a skirt, not unless you want skinned knees!). I'm sloppy and boyish, and look very, very young. My clothes generally scream either 'construction worker lite' or 'tomboy':
vs.
fancy everyday and work
...aka 'accessory change'
On the other hand, my avi is way cooler than I am, and comes across as more mature (I look 15 at all times, no matter what I wear or do). Primarily black clothes do seem to be the common factor here. She projects seriousness and calm, and is total wish fulfillment! She currently has classy, formal clothes (far beyond my irl price range), and vaguely reflects my love of steampunk and astronomy. Plus, she can wear frilly things or fancy clothes and
not look like a little girl playing dress up with mommy's things. The hair is the kind I'd love to have: impractical and lovely and maintenance-free. Her wardrobe is stuff I would wear in a perfect world (where everything
fits!). I'd love to wear clothes like this now, but probably only for short periods of time, because I'd be terrified of wrecking them.
TL;DR: Irl clothes chosen according to cheapness + practicality, avi based on "ooh, pretty, want!"