Okay, here's the deal: I live in Australia so when I pay for my internet it isn't limitless, and after a certain amount of gigabytes downloaded it caps and goes really slow for the rest of the internet month.

I need to know how to control other computers on my home wifi network so they get less internet, because I don't feel its being used fairly.

I don't know if you can help me out..

Probably the easiest way to do it is to setup a linux shit-box as a router, and limiting network traffic to specific IPs and MACs, though either can be circumvented pretty easily.

Check your router's configuration pages, usually they have some sort of acess control stuff