Being an Ozbargainer and a gamer sometimes don't go well with each other so I found a way to get free steam or desura games - it is pretty much an easy grind so this might not be for you.
Warning: I know this is obvious but please do not use your credit card details when doing any of the offers (to be safe).
Trading cards, emoticons, backgrounds and steam wallet credit are also for free (though limited in range and stock) and everything is legal. There is a website called Tremor Games and you do surveys, watch videos and download apps to earn coins and then cash in the coins for the games you want. Tremor source their games from humble bundles and when games are on sale. I've been using them for about 100 days and can say they are legitimate and after that time, I have found ways to maximise the coin income within a short period of coin grinding (will share if people are interested).
I will also list my referral link but you do not have to use my link whatsoever if you are uncomfortable with it, but I would greatly appreciate it if you do. The referrer will get 20% or less of what is made by the referred and the referred will loose absolutely nothing - Tremor gives me coins out of their own pockets.
This is the main link, sign up with them and you are good to go!
My referral link, thanks a million in advance if you decide to sign up using my referral link:
http://www.tremorgames.com/?ref=624530
If there are any questions please let me know and I'll be happy to lend a hand where I can (I'm also in the middle of writing up my own short guide but there are heaps of them on the internet if you do not want to wait).
Have participated in a lot of similar services in the past, so I have sort of an idea of what's going on. Can you give a more complete list of rewards? And how many of them are accessible by Australians? I have grinded for days on a similar service where it turns out I wasn't eligible for the rewards I wanted. Specifics like name of available gift cards, what's in the "lots more" section, etc..