I LOVE Fleet Feet! Are you in Madison, WI? (You can answer me in PM if you don't want to share that info publicly).
Alternatively, if you are in Madison, please visit
www.madparkour.com 
Okay, that hijack out of the way...
Achilles, I wouldn't worry too much about shoes right away. Grip is probably the most important thing but it's best to get a decent pair you can run and exercise in, without spending a whole lot, until you learn more about how you move, parkour-wise. Pretty much any kind of athletic shoe will do the job. If they're wrong for you, you'll know it, and you can make a different choice on the next pair of shoes. But for now, just pick up a pair you like, that feel good on your feet, and start training! Hopefully your PK career will be long enough that you will have plenty of time to quest for just the right pair of shoes for you.
