There are many many factors which are going to affect your conversion ratios.
For example;
– THe casino’s reputation in the market, though especially on the referring website
– The reputation of the software the casino uses
– The quality of the traffic (eg. Fforums vs PPC vs targetted email newsletters)
– Does the website match the advertising that brought the surfer there ?
– How appealing is the landing page is
– How fast is the software download is
– How long the signup process takes
The most important thing is to do lots of TESTING & ANALYSIS. Get some good analytics software, learn it, and use it.
To begin, you can us Google Analytics, or AWstats. They’re both free to use.
This means trying variations on landing pages, signup processes, everything you can think of. Change one thing at a time, then analyse the statistics.
If you want more information on the conversion process, check this site out
http://www.marketingexperiments.com/
To answer your question though… How long is a piece of string ?
A “GOOD” conversion ratio for Banner Click -> Depositing player would be 1:100 – 1:200.