In game terms, Gnosis can be raised by expending five Experiences in any combination of standard Experiences or Arcane Experiences.
In the narrative, Gnosis requires knowledge and understanding. It requires moments of epiphany, study, and experience. Gnosis increases when your character has advanced philosophically, mystically, or academically in such a significant way that she’ll never see the world the same.
While they’re not as influential and life-changing as the Awakening itself, these are moments the character will likely never forget, milestones in her advancement that show clear evolution of thinking, purpose, or identity. Whenever your character increases in Gnosis, consider changing or refining her Virtue or Vice. Definitely look to Aspirations and Obsessions for potential changes. The character doesn’t necessarily become a completely different person, but she’ll come out changed.