idk maybe crest+ (online)
is it worth it?
I bought Crest+ last year, but I wasn't impressed with their resources - they are just (outdated) summaries of the textbook. I will say, however, that their marking services are solid (some markers are better than others, its kinda like a dice roll). If you have a teacher/peer/tutor that can give you good feedback, I wouldn't buy Crest+, it's simply not worth the money imo.
If you were to spend money on eco, buy (good) essay plans from past students - they will save you time in the long run! This is for the HSC course though, prelims are nothing to worry about.