If you are interested in making your own textures, you can modify the textures of the clothing you already have. Make sure you have the surface selection tool active and select the clothing or part of the clothing you want to modify. In the Surfaces (Color) tab, experiment with both the Diffuse Color and Opacity Strength parameters.
If you just want to add dirt and grime, you can just scribble over the top of the Diffuse texture with the appropriate dark colors.
If you want to add holes, you’ll have to work a little harder, but basically you want to make a black-and-white copy of the texture to use for the Opacity parameter. Any part that’s black will be the holes and any part that’s white will keep showing the original texture.
If you want more detail on how to do that or have questions about any part of this, let us know.
If you don’t know where your textures are located, you can find them quickly and easily by clicking on the little picture at the left end of each parameter, write down or remember which filename has a checkmark in front of it, then select the option to browse to the location. Find the file that is being used, then copy it (don’t modify the original!). Make your changes in the copy. Then browse to that copy to select it. If you make repeated changes, remember to select the Refresh tool to make DAZ Studio look for your updates again.