There are two degrees of formal wear, professional attire and formal wear. Formal wear is worn by wedding party members, graduates, and those who attend balls. Professional suits and dresses will get you everywhere else that that you need to be dressed up for but there still needs to be some clarification of what is not professional such as:

Cartoon ties: Taz, and Mickey Mouse are not professional and look silly on otherwise respectable suits.

Denim shirts: surprise, this is a casual item that does go well with a cartoon tie. Together they still make up a casual look.

White socks will stick out badly if worn with professional attire. There are white dress socks, which are only to be worn with the combination of white pants, and white shoes.

Jeans: Although jeans go with most anything they reduce your otherwise professional outfit to casual (no matter how black you think they are).

Athletic jackets may only be worn with athletic or casual outfits.

Running shoes whether athletic or casual will standout like crazy but walking shoes that are worn by restaurant servers and protection officers that are one colour are fine as are orthopedic shoes, and most casual dress shoes (such as Dr. Martens).

Casual pants might be worn with a suit if they are pressed, but they will look weird with dress shoes. They need to be worn with more casual shoes.

Sundresses are fine if you are going to an outdoor wedding or similar outdoor event: however, they tend to look a little out of place in the office.

*Blazers worn over dresses are totally redundant. A dress is dressy, and professional enough to be worn on its own.