Even though the starter kit says its for 5gb, Belong applies it as credit when you activate the sim, and you can choose which ever plan you want. Use a referral/promo code (easy to find) to get an extra $20 credit.
That'll give you $45 credit for just $10 (less if you use a discounted gift card to purchase the starter kit). That's 2 months worth if you choose the 5gb/$25 plan, 4 months if you pick the 1gb/$10 plan. Great for those of us that don't use much mobile data.
This deal was running last week as well, but I saw last night that it's still going and expires next Tuesday.
You can get a referral code from here https://www.ozbargain.com.au/deals/belong.com.au