Go to a online casino supporting bitcoin payment, buy some chips and go to a single zero roulette game, bet all on RED: 47.3% chance to double it

If you remember, the guy used the word 'safest'. I think the safest way it to earn $ with your job or other sources and invest in more btc. Reach 5 btc and save it. A couple years down the line and you know how bright things might just be for you.