You don't even inform them all the requirements to enter. It's not as simple as just send money. There are going to be many tickets you have no idea where they come from. They would be pretty much donating to you. And, even though the source of the random number is fine, since you don't give a time, or how you are going to pick it and people verify it, it's kind of useless.
Why should there be requirements? All i need is the wallet address, and then i random with that.. So it is completely anonymously..
And yeah.. i need a time..