Don't bother trying to earn Diamond with craps or any other pit game. Too expensive.
You need to do it with video poker.
Earn 2500 points in one day, and you will be diamond by July 15th (when they credit the bonus tiers in the spring promo).
If you want diamond sooner you will need just 300 more tier credits anyway, after playing the 2500 tiers in one day and getting the 5000 bonus tiers.
BTW, be aware that becoming diamond will NOT increase your offers, freeplay, or free rooms. It will just give you the guaranteed benefits outlined on the Total Rewards site.
Good luck.
If you want to know the best video poker to play, go to this thread I created on our sister site: http://pokerfraudalert.com/forum/sho...-around-the-US