Gnosticism doesn't believe in 2 gods. It believes that there are a whole pantheon of not-quite-gods, which are emanations of a single (capital-G) God, arranged in a complex hierarchy. They are called aeons and archons and thrones and cherubs and seraphs and archangels and angels and so on and so forth.
The gnostic posits one God who is not of the physical world, and then says that God has some number of emanations or attributes (Grace, Charity, Love, Wisdom, Truth, etc) each of which may be perceived separately, and may act independently, and then mankind perceives these attributes of the Godhead as being (small-g) gods, though really they are part of the larger.
I guess you're talking about the idea of a Demiurge. In gnosticism, the Demiurge is one of these lesser attributes of the Godhead, usually representing the attribute of Order, which tried to put order to the creation, which was at first "formless and void."
Long story short, this emanation of the Godhead is somehow supposed to have lost touch with the rest of the aeons and forgotten they existed, and so it thought itself to be the only god, and represented itself to mankind that way.
Another emanation "Christos" is then thought to have reconciled the Demiurge (who is identified as the OT "Jehovah") into the rest of the Godhead. So in gnosticism, Christ does not reconcile God to man, but rather reconciles an errant self-styled "God" into the larger Godhead.
Jarrod