Do not attempt chronological order on a first read. The short stories assume you know the world and characters from the main trilogy.
Tehanu ends on a question mark, leaving the metaphysics of Earthsea in disarray. The old rules are broken, but new ones have not yet been established. This is where Tales from Earthsea becomes non-optional. Though it is a short story collection, it is not ancillary material. The stories, particularly "The Finder," provide the historical context for the patriarchal takeover of magic that Tehanu critiques. It bridges the gap between the saga's past and its future. order of earthsea books