I'm about to launch a "gambling" website soon which will not take any fees at all and will only live off ads/donations (not sure how well it will go, but we'll see).
It's not going to work. You can't run gambling site and rely on ads and donations.
So the chances to double your money would actually be 50%, not a bit lower. I already have implemented a coin flip mode, where one player creates a new coin flip game and the other joins it, but I also want to create a mode which does not require a second user.
0% house edge PVP coin flip is nice, but you won't get any money from it.
For example slots or roulette, since you can play it alone and don't need to wait for a second player.
Roulette with 0% house edge is roulette without zero
And I could make a mode that you could play alone, but what if someone keeps winning and winning? The money the player wins won't come from someone else, but from me. And I don't want to risk losing everything myselfmyself and then not have enough money to give out.
Then create pvp site only.
I need an idea for a gamemode that a player could play by himself (WITHOUT a house advantage) without there being any other users on the website, while I wouldn't have to risk losing big money myself, because some user got lucky.
Not going to work - for you.
I think this is impossible, but perhaps there is some way, I've been thinking of something like "out of every $10 played, $5 will be lost", but I believe it could be abused and what if someone bets a huge amount once and wins?
Now you are talking about house edge.