If you'd like to know more about what 'type' of gas you need, read this article
In Australia and NZ:
The standard and most common size is a 9kg LPG cylinder, but LPG cylinders are quite common in other sizes right down to around 4kg. Just make sure that the cylinder has a POL connection to attach to the gas hose which is supplied.
Smaller bottles down to around 2kg have also been known to work well but will require adapters to connect to the gas hose we supply.
A common 2kg cylinder will have a 3/8" Threaded outlet, for these you can purchase an adapter like the one in the picture below which will connect to your standard BBQ gas hose.
The left side thread is 3/8" LH (Left Hand) BSP and the right side is a standard POL Connector (to your gas hose).
20 lb Tank
In the United States, you can use a propane tank size right down to around 4.5 lb, the main thing is to make sure it's compatible with the supplied gas hose (it's called a QCC 1 Connection on the bottle side).
1 lb Cylinders:
To use a 1 lb cylinder, you will need a purchase an adapter like this one which will allow you to use your Joolca supplied hose to connect to the smaller cylinder.