The only way to earn 1 BTC or half Bitcoin in a month is only possible to achieve if you have a lot of referrals that are generating passive income for you all day long. There are some people earning a good amount of money this way. If you check Freebitco.in stats for an example, you will see the top referrer players of the site. There is one with more than 80.000 referrals!
Now imagine how much this guy is earning everyday...
The 80,000 referral can be faked, though. Just like how other money making websites fake their leaderboards. It's also possible that the guy with 80,000 referral made all those referrals back then when bitcoins was still starting out. It is also possible that the account with 80,000 referral is the automatic referrer of the sign-ups that didn't put a referrer on their registration form.
1
BTC referral reward will require your referrals to make 10
BTC a month. In the gambling site, they have to lose this much amount of money. Even just finding a guy that's gambling with 1
BTC is quite hard, let alone 10
BTC a month. And if you're going to do this referral program in a faucet site, I really doubt that you'll ever rich that goal.