There isn't too much you can do before school (IMO) as 1. you're starting a new school 2. you don't know how the school goes about folio work/assignments/assessments. However, you could:
- read through the study design
- touch up on the things you learnt last year as you will need to know them for the exam:
3D paraline - oblique, isometric, planometric
3D perspective - one point, two point
3rd angle projection
design principle
design elements
Also, since you have your mind set on communication design, you could perhaps base your unit 3 or 4 folios on 'communication design' (ie, design poster advertisement, create your own branding and portray it in the form of letterheads, envelopes, etc). From this, you would be creating lots of potential pieces to add to the folio you will be showing to RMIT. Most of the folio things gathered to show universities are made towards the end of unit 4.
Hoped that answered your question. If not, feel free to PM and I will be glad to help you.