Hmm, but wouldn't study guides give you...well...a guide? This way you know your ideas aren't in the wrong track?
Your ideas aren't on the wrong track if you can justify them. They want original ideas in the exam for the high scorers, and if you want to be original, you can't be on a track, you have to build your own. Emily and I only ever used the AN study guide about a fortnight before the exam. Oh and actually we read about three pages of the Insight I&B book prior to a context SAC. Ideas should be generated instead of guided. There's nothing really wrong with study guides, but I think if you were aiming for high 40s it'd be better to not be influenced by the ideas everyone else is going to be using.
To give you an example, in my text 'Twelve Angry Men', there were two jurors who were juxtaposed with each other throughout the play - Juror 3 and Juror 8. The former was the antagonist, the latter the protagonist. The play is surrounding the trial of a boy accused of murder. No one ever knows if he did it. At the beginning, 11 people vote guilty, 1 person votes not guilty (Juror

. By the end, it's a unanimous vote for not guilty. There was one point in the play where a juror says:
"If he were sitting ringside at the Dempsey - Firpo fight he'd be telling us Firpo won."
It was in reference to what Juror 8 would be saying, because he was saying the boy was not guilty.
I found this line really interesting whereas everyone else just took it to mean that Firpo lost the fight. What actually happened is Firpo hit Dempsey so hard that Dempsey fell OUT of the ring! It took him thirty seconds to get back into the ring of his own volition (20 seconds more than what would be a knock out) however he wasn't disqualified from the fight. Dempsey later knocked Firpo out in the second round.
To me, in all fairness, Firpo won that fight. Thus, from that, I could say that the playwright utilises a reference to a historical sporting event - highly relevant in the culture of 1950s America - to convey the social differences between the protagonist and the man saying that Dempsey won. This line can be taken as a symbol of the protagonist's tendency to learn towards justice, fairness, and what is right, while the majority of society are happy to challenge nothing and believe what the referee tells them to believe.
That's an original idea you wont' find in a study guide. It's one tiny line that everyone ignored and told me was farfetched when I told them about it. I never put it into any essay but the point is, if I had been using a study guide, I would have read it a few times over and thought "Wow, I know this play so well, I could write on any topic" and I wouldn't have bothered to research that fight. And that goes for the whole play over.
Writing your own would be a lot of effort but it's a really viable way of studying; you're conveying information in a way that needs to be understood by you 'customers' so you are required to control the language very well. You'll be forced to present your ideas in a way that your 'customers' can learn from them, thus you have to identify what YOU think are the themes, what YOU think is the symbolism, what YOU think you can justify. And most importantly, you will talk about the Dempsey - Firpo fight.
(Okay that ended up way longer than I thought it would)