A scratched and dusted wood

First step is to create the base wood shader.
We'll keep things pretty simple and straightforward here. I've used a plain wood texture as diffuse, and added some glossiness variations using a different texture.

Of course, the base shader can be whatever you need.

We will use the same maps to create the scratches material.
The most important channel here is the bump.

As bump map we will use a mix of the scratches diffuse map and a scratch mask, in multiply mode. This way, we will simulate the scratches depth.

Simply put, we will now merge the two materials together using a mask.

This mask will be the multiplication (mix\composite node in multiply mode) between our scratch mask and two dirt maps: a dirt map for the outer edges and a dirt map for the inner edges.

A rendering showing the mask in action: we can see the contribution of our dirt nodes on the edges, as well as the general contribution of the scratch texture mask we have used for the surface.

I do not need to worry about texture mapping or coordinates, as our material ball has been already unwrapped of course.

Finally, we'll be adding some dust effect.

The dust material is a plain grey diffuse with some slight small bump applied.

Let's make the mask now. Dust usually gets on horizontal surfaces, so we'll make use of a directional falloff along Z axis.

To add some variations to the dust mask, we will combine the falloff with the small noise map in subtract mode, and we'll mask them with a larger noise map.