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.
martingale strategy in Bitcoin Dice gambling not 100% safe and it also has its own risk. I think the best method of safe gamble is quit as soon as you get profit and dont risk the next chance.
Also gamble with your profits and keep the original amount intact.