2:1 is about what most people ride. Because you are in Washington, I’m going to go out on a limb and assume that there is no such thing as a flat course.

I am a spinner, so I don’t even mind going just under 2:1. If you go too low, you won’t be able to keep up on flats or long downhills. If you bog down on a steep hill, get off and run.

If you are a masher, don’t run a higher gear; learn how to spin.

Cat5: 40:22 or 40:20/36:18
Cat4: 40:20 or 42:20
Cat3: 40:18 or 42:18
Cat2: 42:18 or 40:16
Cat1: 42:16

For ‘cross, I like to use even chainrings and cogs so you can run narrow-wide, which you can’t do with odd-numbered cogs. Surly cogs are good, Chris King are better. Just make sure and get ones with a wider base, especially if you have an aluminum freehub shell. Wolf tooth and others make narrow-wide chainrings and cogs.