I see that this is an old thread, but here's my 2c worth. A lot of operators operate more than just jets, so another endorsement like a B200 may be worthwhile. Plus there are potentially more B200 jobs around while you're trying to get a jet job.. The operators I know of generally don't recruit straight on to a jet if the applicant has no jet experience, but they will upgrade someone from within the company. Also, unlike some airlines 250 hours most likely won't get you a corporate jet job.
I'd research all of the charter operators and see what types they operate and try to get into a jet via that route. It's also a very small industry where everyone knows someone who knows someone, so that's another hurdle to overcome. I would also research what jets are in Australia and the best resource for this would be the December edition of Australian Aviation as it has all the jet types and operators in one place, though by now there may be some additions.
If I had no endorsements and was going to buy myself an endorsement, I would probably get a Phenom 300 endorsement. The reason being is that there are a few in the country already and that they are a relatively new type oprerating in Australia, so the pilot pool I imagine is pretty small at the moment. But before this I would sound out the current operators to see if there is potentially a job for you.
I hope that this had helped and that others now add their advice.