Two Neutral Colors - Dozens of Options

I get a lot of emails from people who are concerned about building a wardrobe around neutral colors, because they're worried that they will end up looking like everybody else.  If you devote yourself to black, and you live in a major city, that is certainly a valid concern!  But I think that there are more neutral colors around than you immediately think of, and that if you can focus on two colors as your predominant theme, you have dozens of options.

First off, let's choose a palette of possible neutral colors.  This palette is NOT exhaustive, and the colors as they are shown here are NOT intended to reflect the beauty and the depth that the color actually exhibits in three-dimensional garments and accessories.  I tried to consult a number of color website about how to best show the colors that I had in mind, and the advice I found was conflicting...  So we'll have to use our collective imaginations a little bit on this.

 So, if you choose one neutral color as your "foundation" neutral, and then choose another neutral for your "secondary" focus, you have many choices.  First up, you can start with black and then add in any other neutral to use as the basis of your most expensive and pivotal purchases (shoes, handbags, outerwear, etc.)

And from there, the combinations go on and on.  I've numbered them to facilitate commenting; I'm curious as to what combinations hold appeal - I'd love to build some wardrobes around some of the more popular or intriguing choices.