If you're selling your work framed, dont use ikea frames. They dont last through a great deal of handling, from my experience and that of my friends. And the public are slowly cottoning on and recognising them too, so I generally suggest avoiding them. You can save some money but it can just reflect badly on you. It depends on the scale of the show as well, but if you're gonna have a lot of people see your work, pay for quality custom framing. If it's just a small show for a week somewhere, on short notice, you can get away with paying less.

On where to buy I can't really make any australia wide reccomendations, but just find a framer in your area who does what you like and build up a relationship. You can usually negotiate a bulk discount, or maybe some money off if you give them some good publicity. If you're handy you can also just buy the moulding and the required tools and do it yourself, but the initial outlay is hefty.

D-Rings are pretty much a must, make sure you know what hanging system you'll be using.