Re: 50k in bank, want to invest it.
Have you got all your tax from sole trading paid up, or does part of that 50k actually belong to the tax man?
Got any credit card debt, car loan, any other debt? Paying down debt gives you some of the highest and most reliable return.
In order of importance in my eyes:
1. Make sure you don't have any outstanding liabilities - that is a valid and very important point that waimate01 made.
2. Is your business sufficiently capitalised? Is the best way to grow your business to invest in it further? Do you have sufficient funds should business be worse than expected for a prolonged period?
3. Do you have any personal debt - car loans, credit cards, mortgage? Eliminate that.
I wouldn't be in a hurry to invest the money inside super, you won't get to touch it for 30 years so set yourself up for life before worrying about retirement. As a self-employed person in most cases you are under no obligation to make super contributions. You may wish to for the tax deduction if your cashflow allows it, but I wouldn't rush off to do it. Get some advice on that if you haven't already - in your situation you may be obliged to make contributions, or it might be sensible to maximise concessional contributions.
A big hurdle for the self-employed is getting finance to buy a house/investment property/investment loan. Make sure you are on track for the kind of income on paper that you will need to live the lifestyle you want.
Once all of those boxes are ticked then you can start looking at investments outside your business as an attractive proposition. With your house in order determine your focus - income? Or growth? Investing for income you will increase your taxable income from non-employment sources, which is great for allowing you to better your lifestyle or further invest, but it's going to create additional tax payable along the way. Conversely investing for growth you will have less ongoing income and more capital growth, meaning you can choose (largely) when to incur the tax bill by selling some investment assets. Do it in a lean year where you are down on taxable income from business, or when you take time off work to spend with family or on holidays.
Hopefully that gives you something to think about. You're in a position to take a step back and look at what the next 10 years hold for you. Don't rush to dump the money into super or invest it in something that puts your capital at risk.