I think the basic Mormon-Gnostic correlation is in the concept of duality. For the Gnostics, it usually took the form that Jesus and Lucifer are equally powerful opposing forces in the Earth. Some Gnostics took this further and reasoned, since Satan was as powerful as Jesus (some even thought more powerful), they should both be worshipped equally. Usually they viewed the good and evil as two opposing parts of a whole, so that Jesus/Satan together are a duality that opposes itself, creating a conflict that is somehow necessary for the world.
The connection with Mormonism is only in the belief in multiple gods, but specifically in the Mormon view of Jesus and Lucifer as brothers, or two sides of this duality.
I think the basic Mormon/Christian correlation is in the concept of the PRESBYTERIANs tossing JS out on his ear!