The ClarionMag has a heap of stuff that could be helpful.
There are two e-books which could be good.
The Clarion Content section in general.
There is also a bunch of stuff archived from Clarion Foundry:
and here of course!
Keep digging, there is more around.
@Bruce had a book which helped me a great deal when you start getting more into the ABC template/classes, if you go that way. Not sure where to get it these days.