You went home, with nothing more than a black eye. Meaning, you did fine. No matter what, all that truly matters is that you go home when all is said and done. Are you now a "marked man"? Who knows? Unfortunately, the only way you'll really find out for sure is if you get a repeat performance. The question is, what do you do in the meantime?
Prepare yourself, as best you can. No, you can't arm yourself with a tricked out M-4, but if you can get some pepperspray, do it. Learn how to use it, and carry it daily. It will be easier to fight the gang, God forbid, if they have trouble seeing you after catching a face full of pepper. Continue with your martial arts training. No, you're not Jackie Chan, but it sure beats curling up in the fetal position, praying that you'll survive.
As for dress, forget dressing to intimidate. Try dressing for action. Pants the fit, not too loose so as to trip you up or too tight so as to restrict your movements. Shoes that you can run and jump in, as necessary.
AS for the iPod, keep it in the backpack when your out walking. Got a cell phone? Calling for help is not a sign of cowardice, it's a sign of intelligence. How about a couple of textbooks in the backpack. Swing that around and it'll get someones attention pretty quick. Avoidance is good advice. Look into alternate routes. Don't be predictable. Vary your routine as much as possible, to minimize the risk of ambush.
Above all else, think about all of this. And think about it some more. Play "what if" in your mind as much as possible, so that you actually have thought out the options, the possibilities, and your response options. As they say, prior planning prevents p!$$ poor performance.