The white should be minimal. Remember what William Prescott said: “Don’t fire until you see the whites of their nails.“ But seriously, sir, I think one to two millimeters is about right. Much more than that, and you start to look like a pimp or an off-duty drag queen. In some cultures, men grow one nail long, usually on a pinkie, to show they don’t work with their hands or to use as a coke spoon. But I think clean hands and well-groomed nails are enough to prove you’re a gentleman. By the way, even though you think you’re not the type, I think a manicure, like a facial, is a luxury one should treat oneself to at least annually.