I think I'm mostly option 1 w/ a slight inclination towards option 2. The main gnosticism related book I've read was "The Gospel of Judas Iscariot" by Bart D. Ehrman (which I still think was pretty complicated for a 15 year old). If I were to try and find and read the "Manichaean and Mandaean writings, with the Nag Hammadi collection" that you suggested, how likely is it I could find them online through google or a collegiate database? Also, would I need to know/learn other languages besides English (I know the original texts are definitely not English)? I would guess the original text languages would range from Coptic, Arabic, Aramaic, Hebrew and other Middle Eastern languages mostly) (and possibly some East Asian, but I'd guess most European languages besides Latin and Greek would be useless).
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Balance is needed within the universe, can be demonstrated in most/all concepts/things. Black/White, Good/Evil, etc.
All dependent upon your own perspective in your own form of existence, so trust your own gut and live the way YOU want/need to.