https://www.independentreserve.com/ 0.05% fees. XBT,ETH,BCH for AUD. Good security. You have the choice of buying at market price, setting buy limits, sell limits.
Once you've bought into a currency you can set up an Exodus (or Eden for more experienced users) wallet and exhange through their platform (they use shapeshift, super easy but transfer rates aren't the best) Or you can set up a Bittrex account, as mentioned by sbnas and trade through their platform. Very low fees, great altcoin trading in real time at market price. All altcoins use USDT coin, a tether to the USD. Tether claim to have a 1 USDT - 1 USD currency value and in the last 6 months they have been fairly spot on. Have a look into https://www.coinigy.com/ too, there you can view almost, if not, all trading platforms and intergrate their software with Bittrex through their API settings.
I also use Binance which is a great "altcoin only" cryptomarket.