The inversors ROI:
The idea is, each money amount from each inversor that collaborates with the project will be returned by x5 in game-money, you can cash out the money or play in the room to win more.
Example: I collaborate with 1BTC, when the poker room go to live i will get 5 BTC.
How would this even work? Investors can get 5x their investment when the pokerroom goes live, but where will those funds come from?
You're vastly underestimating the costs of this and I really don't think ICO is the way to go with this.
You first need at least some software before you could even think about reaching out to investors.
You're a developer, so start building this first an worry about investors later.