Okay, I looked at a bunch of photos online, and here's what I gleaned:
Toppers : Structure on top of the slouch: tailored men's blazer (AC/DC and Vivienne Westwood) or cropped-length denim jacket or trucker-style jacket. (Blondie. And are we calling these cargo jackets now?) Or oversize 80s denim jacket and push up the sleeves. (Also Blondie)
Seems like you gotta push up the sleeves, whatever your topper.
Legs: If you have tights that have a lace pattern or print, those would look amazing, I think.
I noticed that Debbie Harry always wears these schlumpy, battered-looking pieces - but there is always one impeccable element to her look - and it usually seems to be her makeup. Sometimes her hair as well, but often her hair is teased out and crazy. For makeup, she seems to go for a precisely-exectued rocker eyeliner, or a retro winged eyeliner, and/or a red or deep pink lip.
Also, on all counts, it seems oversize safety pins are an accessory.