The safetiest that i know is to use the faucet bonus don't spend your bitcoin from your wallet just use the faucet bonus and make some profit if you are not lucky to get large amount.. its better to stop so that you can control your self for being greed..
safe way to gamble is just play with the amount of money you can afford. If you go to the supermarket and normally you buy a donut. Do not buy the donut and gamble with that money.