There is no safe method. That said you can try betting a small amount but you will lose in the end. Its the casino owners who make a profit and the players are the losers.
If gambling was a safe method to earn money then people would not study hard and get jobs to earn money.
You have a point in that ,gambling have no safe method but there's a strategy like martingle in Bitcoin Dice gambling its works but not all.
Yes gambling is not safe because we could also suffer a defeat. but there are many strategies, including what you are talking about. In addition we also have to restrict the bets and have control in order not to become addicted.
Strategies like Martingale may seem very promising to new gamblers but trust me if you have a huge bankroll, do it but remember to stop early. If you keep betting using Martingale you will end up a beggar due to the House Edge. Thats why casinos are there and the owners make a profit. No strategy can win against the house that is why it is called an Edge - an Edge over the gambler.