Each individual has different needs. Therefore investigate those texts that interest you most.
However, I do recommend the books on psychology especially, since these lay the groundwork for accessing practical wisdom from experience. Books like Treatise of Revolutionary Psychology, The Great Rebellion, Introduction to Gnosis, Fundamentals of Gnostic Education, are wonderful for this. For an introduction to everything, we cannot forget The Perfect Matrimony!
For thirty years I sought God. But when I looked carefully I found that in reality God was the seeker and I the sought. -Bayazid al-Bastami