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At all times you should own at least two suits, preferably one in navy and the other either a darker grey. You may want to avoid the pinstripe, not everyone can pull it off. Solid colors are your friend here, not be brave. Keep in mind you want to look good, groomed, and professional, but you also don't want to overshadow the man or women interviewing you, so stya away from being too flashy. Your clothes are crucial in proving your confidence, but your experience and words should prove your worth.
Aside from the pinstripe, stay clear of the double-breasted suit as well. Stay current. Aim for a 2 or 3 button cut, please don't go above that, your not trying to look like Prince here. Fabric is somewhat optional, depending on the weather of course. Needless to say do not walk in there in a velvet or leather suit.
You'll want to go with the navy for that all important first interview, then hopefully you get called back for a follow up and then sport the grey. You may be tempted to go with a black suit at this point but fight the urge, black or even tan colored suits aren't really interview appropriate. If a third interview is required do not recycle one you've already worn, buy or borrow a third suit in a similar color. If you get the job chances are you'll need to buy more suits anyway.
Finally, stay away from the casual blazer/sport jacket with dark jeans look. Not for an interview. If you get the job and the dress code permits it, the fine, but not when trying to sell yourself in the beginning.