I firmly believe from experience that no t-shirt looks better than a washed-once American Apparel black T in the right size. It's the closest thing we hackers have to a suit, I think.
By "runners" I assume you mean running shoes? Those aren't all-weather and can't be worn with an actual suit. I've a nice pair of black Doc Martens which shine up wonderfully, and have been treated to be fairly waterproof. They are perfect universal-occasion shoes, and incredibly comfortable.