In accounting you can't just pick and choose which stocks to set your trades against. You use either FIFO (First In, First Out) or LILO (Last In, Last Out) but the tax office prefers FIFO.
You also need to determine if you are going to use Cost Value of Market Value (June 30) for your closing stock.
Trading in shares is a business ... do you have an ABN?
If you're not sure what you're doing then best to get an accountant to do it for you as their expertise and small cost is well worth paying for plus it's also a tax deduction for the next year.
