100 average bet for a 4 hr gaming day will net you approximately 500-800 points based on a very rough approximation and will be subjectively determined by the pitboss. so I would say 20-24 gaming days would get you to diamond which requires 11000 points.

You could obviously speed that rate up by adjusting size of bet or duration of gaming hours/day. That being said chasing a Tier score is not a good idea. That lure is the sole focus of a an entire casino marketing division. Focus on winning and keeping your winnings.