i was thinking about to make a online casino something with dice but not sure is this profitable?
This is very profitable even with small amount of players 
This may be profitable but one need to have huge investments to open up dice site and also you should prove that your site is probably fair. Most important thing is you should gain players trust than only you can make some profit otherwise there is no use of having dice site. To gain users trust, you may need to spend lot of money in advertising. Good luck with your new venture.
Also this market is almost saturated and there are so many established sites are there so if any one coming up with new dice sites than they should add some new features to attract people otherwise I don't think they can get traffic to try there new site. From outside it looks very easy to coming up with new site but it got lot of difficulties to maintain a site and managing user issues. Think twice before coming up with new dice site.