The discovery pass already stated there : by train and coach

Public transport in the 3 cities have their own card. Melbourne = Myki, Sydney = Opal, Gold Coast = Translink.

Maybe you can rent a car. Drive at coast line, stop anywhere you like and stay few days in between cities. Return car in Sydney stay few days. Rent car and drive up to GC. You could see more things that way. Try jucy rentals for budget option. Petrol is less than $1.50 per litre. Price varies in different towns. Hope it helps!

I assumed you can't use because it stated train and coach..

U ask your friends whether do they have myki, opals and brown from them. Top up when u r there. If u buy u can't return the card but to keep it. Jucy shouldn't  be that expensive. If not mistaken $30+ per day. But we book few months before we travel.

If u r traveling within free Tram zone then u don't have to use myki. In Sydney there's no free tram zone.

The last time we stayed in Maze Backpackers. I've searched and its full.. lol.. well City Lodge Hotel is the cheapest RM600++. Maybe you can look at airbnb. There are few 200++ but bit out of town. Its already December tomorrow and you haven't plan and book your trip??

Get Jucy drive on coastline. When you reach cities just return. Don't drive in cities because parking are very pricey! if not just book a coach or train for one way.. check if its cheaper than your package. also better book online.. just in case you cant get ticket when you are there.

aiyo.. then better check airbnb and everyday check on website sometimes they cancel their bookings.. anyways, i love coastlines than cities.. good luck!