Hey,
As you pointed out already economics its self isn't that hard to grasp, but the essays are difficult to write and structure, here are some pointers that I can give that helped me through out my HSC.
1. Look at others essays who have done the HSC in the past and what they do well each time as well as their areas of improvement, the more exposure you have to reading others work the better you can understand the structure. The best way to do this is try and see if you can get your hands on the HSC workbook which is what I did and used those examples, they are often from state rankers and give a good indication of what your writing should be looking like.
2. The introduction, this part of your essay is absolutely CRUCIAL as it is the first impression for the marker in the HSC and when you think about it first impressions are quite important. So in my intro's I would ANSWER THE QUESTION STRAIGHT AWAY giving my view on the question and then defining key terms and then further elaborating on my view point.
3. The BODY this has to be the main component of your essay, it must be in-depth with continuous analysis. The best way I thought to have in depth analysis was to imagine the marker has only the most minimal knowledge of economics and as they read my essay anything that is not explained completely, backed up with evidence would fly straight past them. In your body it is essential that you continuously link each piece of evidence or analysis back to the question to ensure it is well answered.
Moreover you need to explain things from start to finish ie you could say that high unemployment -> low economic growth as a point, but to ensure you explain everything you should explain each step ie high unemployment -> leads to lower MPC as people have less money to spend -> which in turn lowers consumption -> which in turn lowers AD and economic growth.
4. Conclusion this must be concise enough to reiterate all your points and reaffirm your stance on the question.
I hope this helps.