Interesting questions. What are you most interesting in getting from this study? That is, are you most interested in theology/religious thought, discursive philosophy, or wisdom teaching/gnosis?
I would personally say that most pre-modern religious, philosophical, and literary/mythological corpora are worth reading and studying (except perhaps the Epicureans, Academics, and Charvaka) and certainly the Avesta and the Chinese classics are. You won't find much discursive philosophy in either, but you will find interesting and, often, profound moral and spiritual teaching and symbolism.
