[ChkbookMechanic]

I don't think showing up in an expensive suit is going to hurt your chances. I just bought a suit a few months ago, and the style is toward the single-breasted, 2-button sleek, form fitting design. Don't be afraid to try on a lot of suits because you've got to look good and feel good in it.

Color-wise I'd go with:
-darker color (dark navy, black, dark gray) suit.
-white shirt w/ french cuffs (and cuff links!)
-slim / skinny tie with a flash of color to offset the dark suit (think red with a nice, subdued design ).
-Shoe-wise, wingtips or a sleek dress shoe in black.
-make sure: belt, shoes and socks are all of the same color, too.