An agnostic is one who does not know.
A gnostic is one who knows.
In early Christianity, gnostics were those who based their faith and beliefs on an inner knowledge or awareness of the Christ. They considered it to be a first-hand experience of the presence of God within, the Christ, the spirit of Jesus, etc. For them, this experience of knowing had more spiritual authority than the historical record of Jesus Christ in the new testament. They felt that their inner experience or inspiration trumped the authority vested in the hierarchy of the newly formed Christian Church. Their spirituality was at odds with their relligion; so their church eliminated them and almost all record of their teachings.
Some of the manuscripts in the Nag Hamadi Library are the only gnostic writings we are aware of. Prior to their discovery we only knew what was written about them and against them; not what they said about the Christ or his teachings. Not everything in the Nag Hamadi collection is gnostic, but all of it was banned material, taken from a monastery and buried rather than burned as orderd. We owe an unknown monk in a monastery library a debt of gratitude for his love of the written word.
The New Thought movement is made up of gnostics, and since you've read this far I suspect you will find the Gospel of Thomas very interesting. You may not care for all of it, or for other gnostic gospels; but that is the essence of what it means to be a gnostic: you are an independent thinker, finding an inner truth and reality.