Aim for a certificate 4 or higher at TAFE , as this will boost your chances of getting into uws the following year. You may also sit the STAT test (special tertiary admission test) which is administered by UAC. If you score well in this test, you may get into university with it. Basically there are 4 criteria they look at in terms of applying for university when you're not a current year 12 student. These are:
1) Secondary studies, aka HSC etc
2)Tertiary studies, eg) TAFE certificate 4 or higher, or equivalent at a private college, institution
3) Work experience. Has to be a minimum of 1 year, full time and paid but does not have to be related to the course you are applying for.
4) The STAT test
Basically, each of the four criteria will be given a rank out of 100, quite similar to the UAI for HSC students. The highest rank out of these 4 criteria will then be used with your application.
You could could also check out doing Unitrack, which is a program where your not actually enrolled in a degree program as such, but rather individual units ( maximum of 2 per semester) If you go well in these units/subjects, you can use them with your application and demonstrate that you can work in a university environment. (they could fall under the 'tertiary studies' criteria)