1) Do not let the developers have access to provably fair, or similar feature of the site. MD was screwed this way because their devs knew the seed generation/could access the adminstration.
2) Be sure to have at least 20 BTC when making a gambling site, if not, you're going to have a hard time making profits
3) Be sure to make it provably fair, anything else(except softswiss etc, but a you said, you need a new idea) might be considered rigged and when the complaints later come, you have no way of proving the site is not rigged
Good luck
As I understand it, 20 BTC startup wil not be enough.
You would need much more than 20 BTC, as I understand that you need to get a license to run a gambling site in most jurisdictions. This means, you must go to court in order to get your licence: you need a good solicitor too to sell your case, otherwise you are acting illegally to create a site without a licence that envolves gambling.
20 BTC is not enough but why does he need a license? did he mention that he wants to open a fiat casino? this is a bitcoin forum and I would assume that he meant a bitcoin game. Op please correct me if I am wrong
Even bitcoin casinos require licenses if you reside in the US, or other jurisdictions that require this. The license is EXPENSIVE too, and you would need heavy funds and a thorough plan for this.
OP wanted something unique though, and probably for exactly this reason.. To avoid the legislation that's against you nonsensically and to not be a redundant clone of anything else.