I forgotten a site where I've invested only 1mbtc and got 8mbtc. If anyone knows about it please let me know. also similar sites like that will do. Thanks for reading.
Topic title is somehow misleading when we are reading on the OP queries. Some users already gave you the website on which you could able to multiply your bet on a particular winning. Im not really awared on these kind of sites but they are good though but winning chances are too slim.
To win money from any gambling site you just need a luck not a particular site. So I don't think any particular site or strategies will bring money to gamblers in the long run so just gamble for some time to enjoy these exciting games instead worrying about profits.