Grade 2 is best for getting work. Junior grade 3 is next to useless.
If your under 30 a working holiday visa would be the go, work in a rural area and they'll give you a extra year on your visa.
Sponsorships are VERY RARE, however not unheard of.(for valuable people with Aussie licences already)
I would come here if you want and can afford a working holiday with a small chance of getting a aviation job. If your only interested in flying work and want to progress your career, the chances are against you and your setting yourself up for a world of hurt.