Australians generally expect a "high" level of carbonation. When bottling this generally works out to be about 8g/L of sucrose, which is approximately 6g per longneck (1 teaspoon) or 3g per stubby (1/2 teaspoon) or 180g per 23L batch. When kegging, you need to use less sugar (due to less headspace on average I think) so 120g/19L is probably appropriate, which works out to be 54g/9L or 72g/12L.
Note that bulk priming can be used equally well when bottling as when kegging. You just boil up the sugar in some water (normally a cup or a bit more than a cup) and add this to a sanitised fermenter, and rack the beer on top. The swirling action of the beer as it racks onto the sugar stirs it in, and you can then bottle and cap the beer without having to prime individual bottles. Bottle priming vs bulk priming is really just a preference thing, people just do what they find easier.
Once you have carbonated your beer in the keg, you need some way to force it out of the tap so you can drink it. That's where the CO2 chargers come in. You will need about four CO2 bulbs to force out a 19L keg, so I'd guess about 2 to 3 bulbs for a 9 or 12L keg. You can't really carbonate beer with the chargers as they simply don't contain enough CO2 and they're relatively expensive. At least you can recycle them with your normal steel cans.
Note that I'm quoting all the sugar weights for dextrose. Sucrose is 10% more fermentable by weight (dextrose contains a molecule of water in its crystal lattice for every molecule of sugar, whereas sucrose does not). So to convert the weights to sucrose, multiply by 0.9 (if you can be bothered, I guess it's not that significant).
Anyhoo, if you're interested in learning a bit more about priming, check out:
Essential Guide to Bulk Priming