1) Calm down. In every way, panicking will not help. Take some deep breaths, and maybe go somewhere quiet to deal with/process the news. Remember that you've still achieved the great milestone of finishing year 12 and placing in the top x% of the state. Once you're calm, consider the following steps.
2) You still have 2 more rounds of offers! Many students turn down their offers for various reasons, you could get lucky in the next couple of weeks.
3) If that fails, it's time for what I call "the backdoor plans". You can, almost without fail, make it into your course through alternate means,
4) You can take a gap year and enrol through VTAC again with the same ENTER and hope the clearly-in for your required course goes down.
5) You can take a 'gap' year and do another 1 or 2 VCE subjects or the UMAT for med etc. to bolster your ENTER. You can work part time while you do this, and earn some cash whilst boosting your ENTER into the course you want.
6) You can enrol in the same course at a university with a lower ENTER requirement, work hard, and transfer into 2nd year of the same course at your university of choice (you may have to repeat some subjects, however depending on the university)
7) You can enrol in a similar course at the same university, work hard, get a good average and transfer across to that course. E.g. for Law at Monash, you can go into a bachelor of Arts which requires ~80ish ENTER, and then if you get a 78+ average you're almost guaranteed of a transfer to Law/Arts.

DO. NOT. DESPAIR. Post on VN and ask advice, so many people have been in your position and can advise you! Keep your chin up, and you'll get where you want to go
Finally, MAKE SURE TO ACCEPT YOUR OFFER, NO MATTER WHAT. For all of those steps, you can do it while accepting your offer. If you want to take a GAP year, you can defer the place and work on your VCE/apply through VTAC again. If you're waiting for your next round offer, accepting DOES NOT PREVENT YOU FROM GAINING HIGHER PREFERENCE OFFERS. Just accept and then wait and see what to do. You can ALWAYS reject your offer without penalty until 31st March, but after about a week (somebody correct me if this is wrong), you are no longer able to accept your first round over. You have nothing to lose by accepting.
Good luck to all, and I hope you get all the offers of your wildest dreams. For those who don't, however, I hope this post helps you, and don't lose hope!
Post on the VTAC board for specific advice. People will help you! I know I'll be advising all of the engineering queries.