Does Gatsby suffer for the sins of others? No, it's pretty much his own sins. But doesn't he die for Tom Buchanan's affair? Yes, but it's not like Gatsby took on that suffering willingly.
No. Gatsby is not a Christ figure. Your teacher is crazy if he or she thinks that.
Gatsby represents longing. He longs for Daisy, for wealth, to reinvent himself, to be important, but in the end he ends up with false friends and staring at a light at the end of a dock owned by a guy who never worked a day in his life for his money, but ended up with the mansion, the girl and the American Dream by inheriting it.
Christ, on the other hand, represents the union of God and man in order to save men from their sins, and lead them to a resurrected life in Him. Christ represents fulfillment, not longing. Christ is the opposite of Gatsby.
There's your term paper theme. Enjoy.
PS: If your teacher disagrees and you haven't plagiarized this, then send him or her my way.
UPDATE ON SEPT. 22: Another hit for "Jay Gatsby as a Christ figure." Is there a class really assigned this nonsensical topic?