It is doubtful that you’ll be arrested if you play at an online casino if you are based in the US. In many states now there are licensed online casinos where you can play. You are free to play at online casinos based in other countries or have licences from non-US licensing bodies, like Curaçao eGaming.
The rules of craps may seem hard at first, but once they're understood, it's so easy. Played with a couple of standard six-sided dice, you can bet on the outcome of the roll.