There are any ways to earn 0.5 BTC. You can earn it by doing signature campaign, trading, or gambling. But of course it will take some time to earn it until 0.5 BTC.
Maybe faster way to earn it is by doing full-time job that pay with bitcoin.
I think it would be better for him to avoid gambling if he doesn't want to lose all what he has earned so far from other ways of earnings, because gambling is not a source of income, he cannot earn profits from it but he will just end up losing what he has earned by doing some work elsewhere.
I agree because gambling is just for fun and we don't need to take it seriously because there is a high risk of getting loss of our coin if we continue gambling.