Inappropriate clothes or grooming can invalidate the individual and even the entire department or company. At the very least, an unsuitable image creates a barrier to immediate communication. Clothes don't have to be expensive, but they must fit. Be sure to figure the cost of appropriate alterations when shopping. Ill-fitting clothing, no matter how costly or stylish, is unprofessional.
Men often wear clothes too small, women too large.
Men buy clothes, expecting them to last forever. What worked five years ago doesn't fit now. Men end up with belts looped below the belly, pants and sleeves too short, jacket buttons too high above the stomach. Womens' skirt lengths shouldn't hit an unattractive part of the leg, and pants shouldn't bag or pull. Go easy on accessories.