If you posted, “I have 0.5 extra btc that I’m willing to lose.” Then I would help you find somewhere to gamble it and maybe become a lucky winner. Any “investment” has the potential to take all of your btc away.

A sound investment for someone without much money is to hold what you have and add any extra fiat to that slowly as you earn it through a regular job. Take all the money that you would rot your teeth with every month (buying sweets and soft drinks) and add that to your btc holdings. Pick a thing that you spend money on every month that you don’t really need and buy bitcoin instead (I suggest dumping your girlfriend, you wouldn’t believe how much money you can save with that one alone). Bitcoin has the potential to increase by 100%, 200%, 300% or more in a short time. That’s the least risky investment you will find around here.