You just can't beat a crisp white shirt. I always think of the graceful and timeless Christy Turlington who is known for her fresh white shirt aesthetic.
When I'm stuck for what to wear, I think classic, and you can't get more classic or chic than a white shirt. It's one of the most versatile pieces of clothing I know- evoke a safari feel when worn with wide pants, be super slick and pair it with cigarette pants, or take it up a notch and power dress it tucked into a pencil skirt.
The white shirt will take you everywhere, effortlessly.
I go for ones with a bit of structure because they'll lend themselves to all of the above looks most easily. Add a smoking jacket to your wardrobe à la YSL at some stage too, and you'll be smoking for any occasion.