The hourly bonus. Wait for it or set your iPhone time ahead. Go to your settings, then date and time, and then set the phone an hour ahead, then go and collect your bonus. Keep repeating this for as many times as you want the bonus.
You can also connect via Facebook to get 500 free coins in Slots Journey.
You can increase your odds of winning by betting the maximum amount of coins. The more lines you have and the more coins you bet, the more ways you have to win. Each time you beat a level and unlock more lines and bigger bets, opt in every time and don’t opt out.