Free casinos primarily attract bonus hunters. Bonus hunters are people who earn by no deposit sign-up bonuses in for example free online machine. They try to have a decent income without spending a dime of their money. But the casino is also not fools. The administration strongly prevents such cases and discards bonus hunters. If the level of your game is an amateur it is unlikely to get a lot of money just for bonuses in free casino slots without opening real money deposit.