There are some good mobile deals around, although I would only go Telstra, or someone like Aldi who onsell Telstra wholesale.
If you were to go down this path, I'd make sure all updates are turned off whilst using your mobile connection (Windows 10 has this feature, turn off windows updates on metered connections).
You can use most smartphones and set it up as a mobile hotspot, so you computer connects to the phone via wireless and uses the internet connection from the mobile phone, or tablet if you have a 3g/4g enabled device.
I have Aldi mobile, and have gamed using it, although depending on your mobile coverage, it may not be as good, but it would be worth testing out.
If its something you want to look into more, PM me and we can have a chat, maybe someone else might have something to add to the conversation.