You Don't Know A Thing About Clothes
Ok, so you don't know a damn thing about clothes. All the more reason to actually hit the stores and talk to people that do. Sales associates are your best friends, and for higher-end department stores and boutiques, will do a good job of teaching you the basics about how stuff should fit.
Don't be scared to learn about clothes. You really don't need to know much. You learn about all your big investments before making that big splurge right? You can mouth off the stats of the latest Apple product, the car you wanna buy, and the TV you're lusting after, so why should the luxury gear you cop be any different?