I'd say ask a stock broker and not those on a site like this one. But if I was you I'd start off by investing no more than 1/4 of your available cash, and then go from there if you're doing okay. Of that $50,000 I'd be putting 80% of that in top blue chip shares that pay dividends, but make sure you balance your portfolio across most sectors. That is the most critical, as your portfolio will much more balanced.
In doing that you'll ensure that when you have bad day you'll still have one or 2 stocks doing okay, and you'll have good days where some will be doing badly. However, long term they'll move together and hopefully upwards - that's the plan.
Most here are bullish on gold, followed by energy and then the mining sector. All are great, but generally go up and down together. Opposite to these is the financial sector with many still too chicken to touch banks. For me there's no better reason to get into these than the fear factor. This is the most oversold sector, but with the potential to recover the most. Throw in some stocks from the health sector, consumer goods, utilities, industrials if you like.
Then there's the defensive stocks that people turn to when the market goes down, and they are Telstra, Fosters, Coca Cola Amatil, CSL, Woolworths, Metcash, Newcrest etc.
Start with those from the ASX top 20 and work down from there. BHP, all the 4 big banks, RIO, WPL, WOW, TLS, CSL these are real top 20 heavyweights that offer great value. Many here will tell you to buy into crazy stocks like BMN, ADY, CVI - for these stocks I say spend no more than 1% of your total capital.
Once into stocks, you'll be bombarded with a plethora of emotions never experienced before lol. Ultimately you'll come to a point where you want to sell. Our aim here is to only sell when you need the cash and that it has greatly appreciated in value. That's the in the perfect world. Once in you'll be thinking whether to stay in or not as the market sells off at times. By only selling stocks when they go down in value you will never make money. If you choose to only sell stocks when they are in profit zone you will never loose money. The motivation is important - try to avoid selling off when others are. The market has gone down a long way and most don't believe there's much left to fall down to. Buying into the ASX top 20 gives you the confidence to hold on a lot more.
To finish off, my final recommendation is the following. Whatever amount you decide to invest, do not invest it all in one hit! Slowly feed yourself into the market over several months. Avoid buying into greed, but be brave enough to buy into fear. Stay firm, don't listen to the noisy media chooks. Get the feel of it all, be quietly confident in your approach, without trying to be too smart. By buying into top 20 stocks when the so called 'smart investors' are selling due to fear, then you're almost guaranteed to come out of this at the other end as a winner. You buy wholesale and then sell at retail.