You could always email your teacher regarding the tools etc, it would be better knowing something than nothing
Gatsby was the bane of my life last year. I was so bad at it, in 1 essay my mark was "3-30/60". Obviously she didn't want to dishearten me, but yeah, I was awful at it. My highest mark was 47 before the exam, and I thought that was incredible! I sat down the day before the exam, I read the entire novel again and wikipedia was my best friend; that's the only way I got the A.
From what I can remember, we covered themes like the American Dream, Frontiersmen, Symbolism/Realism (all the genres really) etc, I think your best bet is to look what the Agenda for Study says and focus your notes around what it has on it.
Context wise, I looked at Fitzgerald's life, Zelda, how him and Zelda can be compared and contrasted to Gatsby and Daisy, new money and old money (and Fitzgerald's embarrassment over his family's money situation when at University etc). Again, the Agenda for Study will really help you out with what to do research on
(this research doesn't need to be too detailed either; wikipedia is good enough!).
Just make sure you've got a good argument, it's well structured (4/5/6 points) with a good direction, and integrate quotes and context in along the way, making sure to really drain every quote language and tone wise! Make sure you mention structure too
Here's the Agenda for Study if you don't have access to it already:
http://www.ccea.org.uk/english_literature/ (it's under GCE, Support Materials, AS2)