I am trying to  work with the Dragonia model. I have installed all the above downloads except the one that is for non-commercial use only.
I can load the Dragonia model even though there is nothing in my data/DAZ3D/ folder relating to the models. I then loaded the dress from the My DAZ 3D Folder as I can't see anything for !!3S Poetry under either Genesis 2 Female of Genesis 3 Female.

The big problem comes when I try to load a shader from Shader Presets/!!3D Poetry/Dragania. I get the message in the screen shot above.

I have been through all the downloads and checked them against what is in the relevant folders under My DAZ3D Library on my desktop. All files are present and accounted for.

So.... Where do I find the above files and the ones to install into data/DAZ3d/Genesis/...., data/DAZ3d/Genesis 2/.... and data/DAZ3d/Genesis 3/ ....?

From what I see in your screencap, you have several layers of subfolders in the hierarchy; do you have an external HD entitled K:?

The Data and Runtime folders, if prsent, and any other folders at the same level of the zip (e.g. People) go in the folder you have selected as a content directory. The when DS finds a relative path like /Runtime/Textures/somethingtoolongtotranscribe/image.jpg in a materials file it will stick that after each content directory in turn until it finds a match or runs out of content directories to check. So, either that is not where they are or the creatorr has made the mistake of saving with an absolute path (starting with the drive letter) which will not work with any other directory set up.

I do have an external drive labelled K:. It houses my Music files. It does not have folders called 11AMS11 or AMS Studios.

The files are all in the correct directories according to their listing in the expanded .zip files.

I can verify that there is an absolute path mistakenly left in the .duf files. That's what's causing the error. You have two alternatives to correct the mistake: either change the texture path in the surface tab for both the diffuse and bump channels and resave the assets back to the Daz library, or physically edit the .duf files in Notepad++ and resave the corrections. I opted for the latter method; it is tedious looking through the script, but I avoided going through the additional steps to save it back into DS.