If you want to compete with the larger guys, and have a max win of around 10BTC (or maybe ever larger), and assuming you don't want to risk too much of your bankroll, you will need at least a 4000 BTC bankroll.
Also, don't forget that the amount is probably even higher, because there are all kind of expences that you have to pay.
i think 10btc not enough for bankroll , if you start with this amount your website coudl be dead since the first days , because there's too many wabsite and you have to be with Tops and the best way to be is having great bankroll and max win around must be high
It's not enough and if I want to make a dice site I'll consider the saturated market for dice sites and casino's. But if you insist and you have the guts to pursue this project of yours I'm not going to stop you. Why not try to think of something new that's not yet being offered by most of the casino's and I guess it's better for you to stay with that idea. Anyway still good luck to your project.