If you're looking to trade a high volume of cryptocurrency, use BTC Markets or Independent Reserve (see my BTC Markets review and Independent Reserve review). BTC Markets and Independent Reserve are the biggest exchanges in Australia and they have the highest trading volume for Bitcoin and Ethereum, which means their spreads (i.e. the difference between buyer bids and seller asks) are low and it's much easier to buy and sell a large volume of cryptocurrency on them (if it's a major cryptocurrency like Bitcoin, at least). I personally mostly trade on Independent Reserve, but if you're really a big trader BTC Markets is better because their fees go way down if you're trading high volume.