A reader requested a "day to night look." It really doesn't get much easier than this - start with a cocktail dress with a long enough hemline for work, and just add a blazer for day. For night, add a clutch (and switch your shoes if you want), and you're ready to party!
Occasion: Work, then dinner/drinks
Dress: Express, $10 (bought many years ago)
Necklace: Banana Republic, $40
Shoes: Banana Republic, $22
Blazer: Banana Republic, $50