Investing with BTC0.5 is not as good to me, we need to put a decent amount which means a bigger amount to get a good return, honestly I tried with small investment and it didn't work out because i was tired of waiting which resulted to withdrawing it just lately. Now, my activity is more focus in buying cheap alts since bitcoin has increase its value substantially.

0.5 bitcoins isn't a huge amount, just 800$ or so. With an investment like that he won't earn much money, because income investments only worth if you invest real huge amounts, like 2 bitcoins or more.
Choosing a trusted casino it's hard to be scammed, however it's unpredictable to know how much profit he can earn from this, there isn't a fixed rate.

Ofcourse here many numbers of the casinos are available to Invest ( you can see in most of the topics like moneypot cryptogame etc) .
But here u would like to tell you that this just risk like gambling , I would be more better to make Gambling with your bitcoin instead of Investment , Because if you will loss then all your deposit will.loss , but I the gambler loss then you will make a small penny of the earning .
So here this will be more better that you should give time for the trading , Just research about the best best altcoins for long time and then after buy put then at sell in advance , so in this way you will never face any problem that have no time for Trading . I am also doing the same as a side job with my teaching job .

Does it mean a gambling site will not be consistent with its capabilities of providing benefits to its investors ? I just wonder it will be possible when a gambling site's bankroll will be growing along with number of gamblers who will be interested in adding bankroll for gambling continuously. Maybe it is not happening in real life.

Fortunately, we are the bitcoin gamblers having some very good opportunities which will be paying consistently unlike some many other industries where we could not find the any single legit opportunities. PTC industry must be one good example here. My suggestion is also we should not rush for making fast money. Consistency and patience will pay better.

Investments are totally ok, it can possibly generate you 1% a month which is actually good. Since investment gurus will always state that a 10% per year growth in your wealth is already ideal. If you do get 1% per month then you are actually getting 12% a year and that is totally good investment already.

I invite you to join gambling  site which shown on my signature.If i have a money in btc wallet  i prefer to play live casinos with that money. Just check their live blackjack games and you will find your way. Better use martingale strategy or do some arrangements to your money management  also dont forget to enjoy from gambling. There is a reason behind it, if you cant enjoy whatever game you gamble you cant win in long run. Enjoy and happy earnings