I don't remember when I first read Borges, but he was part of the mix in American "postmodernism" (metafiction) and behind or underneath the Latin American boom. Everyone had read Labyrinths, a book that does not exist in Spanish. I really went to school with Borges, reading all of it, poetry and prose, going back to works that he later suppressed, etc..., and reading parts of what he had read. I am more Borgesian than Borges.
Borges is a great innovator whose theory of literature is that innovation does not exist. Everything has already been invented. His beef against Hispanic avant-garde poetry was the narrow emphasis on the creation of new metaphors. For B, a valid metaphor had to be one of a narrow set of universal metaphors. You couldn't just arbitrarily forge new ones. In this he anticipates the cognitive science approach to metaphor developed much later. He is also one of the main translation theorists, with a perspective more useful, even, than Benjamin.
I won't have many posts on individual writers in this series, but I believe Borges was formative for me.