You really should never wear a black suit to an interview. Traditionally, they are reserved for funerals or mobsters...navy and gray should be interview suits (no pinstripes though). For suits, Thick as Thieves makes a great MTM suit for about 425 dollars and they do a conservative interview style.
Avoid square toed shoes...they look terrible...invest in a classic pair of Allen Edmonds Park Avenues (Black) Dont wear brown shoes to an interview.
http://www.amazon.com/Allen-Edmonds-Mens-Avenue-Oxford/dp/B000H1D53G
Shirt, for an interview, you should usually be white or light blue...avoid flashy ties instead opting for more classic/"preppy" ties (j crew on the lower end brioni or another seven fold silk on the higher end....)
Add a white pocket square in a tv fold.
Do not wear a tie bar or tie pin to interviews.
Most importantly, take the suit to a quality tailor and make sure it fits. Also, make sure to shine your shoes.