The key is to not stand out.
Most interviewees (guys) will be in a suit. Now if your blazer and pants makes you look good, then you can probably get away with it. A good rule of thumb is to ask yourself/wife/friend this: can I go to a job interview in a white-collar profession at a Fortune-500 wearing this? If you decide on the blazer/pant combo, just make sure you don't look like a kid in a school uniform (or attend a prep school)
A suit is a good investment. Not only will you use it for interviews, but you can use it for other events which may pop up in life ... and if you don't change in size, you can use it for your residency interviews.
But do some research beforehand on what type of suit you want. It's hard to find a good quality suit for cheap ... easier to find a cheap suit for cheap. 100% wool is a must. Threadcounts, single v double v no vents, # of buttons, single v double breast, are important choices you will have to make.
Make sure it fits you correctly ... properly taylored. Now you don't need to have it custom-made for you, but at least get measured by a taylor and have him/her make the necessary adjustments.
Polish and shine your shoes. People who are ex-military and people from an older generation will appreciate a nice polished shoe. Will start you off on the right feet
🙂
Is a $500+ suit necessary? Probably not. If you decide on a suit that is $500+, you can always ask your friend for a loan and pay it back later. It's an investment in your future. On the otherhand, most $99 suit are made from cheap material (or different cloths woven together). At this stage, you want a nice suit that looks good, fits good, and can be worned for the next 4-8 years as needed. Something in the $200-$400 range would be perfect. Having it taylored can range from $20-$100+, depending on the taylor and what's being done.
Try these sites to get things started
Men's Wearhouse - nice selection, decent suits
http://www.menswearhouse.com/index.jsp
Here's an AskMen article on what to look for in a suit. Remember, you don't need to have it custom-made. One off the rack and adjusted by a taylor will be just fine.
http://www.askmen.com/fashion/fashiontip/34_fashion_advice.html
Here is a recent CNN Money article on how to pick a suit - most of the advise really doesn't apply to this situation but I added it anyway in case anyone is interested
http://money.cnn.com/2006/03/30/pf/goodlife_fortune/index.htm
Princeton's undergraduate career service - what to wear for interviews (men and women)
http://web.princeton.edu/sites/career/Undergrad/JobSearch/dress_code.html
Good luck.