Ehm, just look at it this way. You have to look smart and sharp.
You are going to tell the people that you are the one 'suited' for the job. It's not always so that a dark suit with a plain tie works for anyone. Most of the time it works tho. Just don't walk in with a brown suit out of the seventies
Look around on the street at some managers or something, then try some suits on at the local tailor perhaps? I have a Boss and Armani suit. Both not really cheap, but hopefully they will pay off.
Get a second opinion from someone that joins you on the suit hunting
