What is meant by the great chain of being in Macbeth and what order are the owl, a rose, the porter, fleance, a grizzly bear, a gold nugget, an angel, and ross in the play?

The Great Chain of Being is the belief that existence was hierarchical in nature, with power and authority radiating downwards from God. I would think your order might be:

Angel

Ross

Fleance

Porter

gold

Animals

plants