You should not invest it at all because why should you, with holding it for a long term you can maybe become a rich man.
Its for Security purposes because we do not know how will be the money value tomorrow but for me,
My strategy will be if I have 15 bitcoins I will sell all the coin when the bitcoin hits 1k$ and instead of buying bitcoins back with the cash I will buy some property or gold.
Though, Property is the best option.
Gambling- No, Never I'm not going to bet my bitcoins because its high risk and I don't want to lose such big amount.
Forex- I had a partner who does Forex trading but no I'm not going to invest in this too.
And yes I will use 1 Bitcoin for my personal use.
to me i think the best option is to hold it and not to use it any where because the price of bitcoin is increasing from time to time and still there good potential in the price of bitcoin therefore i think you should hold bitcoin and not to invest it anywhere.