Tim Riley - Year 12 Economics
Tim Dixon n John O'Mahony - Australia in the Global Economy
Jeremy Buujtjens - Excel Hsc Economics
John Bulmer - Updated Economics
Dixon is best for introducing topics and essential if your teacher doesn't thoroughly cover the course. Bulmer and Riley are more in depth and complex - they will give you the understanding and knowledge to ace the essays.
Study guides for ecos are useless IMHO - you are much better off making your own summaries - or - using the ones in Dixon.
I used to rave about Dixon but now I find that one is just too convoluted and long-winded. I have stuck to Riley for most of the year and plan to keep doing so
Dont know about Bulmer but Riley is updated every year. The thoery remians the same but the stats are changed. You could always use a recent one rather than buying the new on and just gather the stats form somewhere else (namely Leading Edge resources )