The safest way to gamble is to start gambling without depositing. At least, if you lose, you just lost time.
What I like to do is to use XAPO Faucets, once I reached the minimum amount I can send to another bitcoin adress (5500 satoshis) I put them on a multiple events sports bet I make on DirectBet.
Even if the odd is around 2. I make a "safest" bets possible so I can reach higher amounts pretty fast.
Just imagine you bet on a 2x payout sports bet, everyday starting with 0.000055.
In a week (7 days) you get: 0.000055*2^7=0.00704 bitcoins. Then 5 days after 0.00704*2^5=0.22528.
If you lose, no problem, just do it again, until you reach a great amount. And learn to stop. Do not get greedy.
Too far fetched, too far fetched. That's winning 12 times in a row and you also have to wait 12 days. To reach 12 times in a row win, it will take a lot of time, it might even take you years before you get 0.22528BTC when you can just look for work instead. Tbh, you can easily earn that by grinding and hustling in real life. Even though that method doesn't require that much effort/actions, the chances of you to actually do that is so close to zero.