I would recommend visiting 5th Avenue.
You'll be surrounded with lots of stores to choose from.
After cruising 5th Avenue, go downtown to Soho (South Of Houston).
There, you'll find more stores to visit.
In Noho (North Of Houston) they recently made a Huge Adidas Store
that once was a Car Wash.
Noho, is more Hip Hop clothing, and, Soho is more European clothing.
With the exception of Urban Oufitters...