Re: I have 12 BTC in my Account, How should I invest this??
Keep 12 BTC and wait... 
That will depend on your view of Bitcoin and where things are headed. The most bullish on Bitcoin adamantly believe Bitcoin will serve as the world's payment rail and that Bitcoin will unearth all existing financial and legal systems. Those bullish expect Bitcoin to hit $10k or $100k+ in the next few years.
Best thing that he can do is to just hold on to them and wait for the best price so that he can sell and make money with it.That will depend on your view of Bitcoin and where things are headed. The most bullish on Bitcoin adamantly believe Bitcoin will serve as the world's payment rail and that Bitcoin will unearth all existing financial and legal systems. Those bullish expect Bitcoin to hit $10k or $100k+ in the next few years.
That is what I would do at least but if he wants to sell now he can also do that.
If you are satisfied with current price you can sell some of them, but I will prefer to trade with them so that I can have more number of coins for future to earn extra profits from it.