Minimum bet is .01, your first bet is a tip.
"Only use wallets that allow you to receive Bitcoin from the same address you sent from. If you're not sure, test with .001 Bitcoins. If you get nothing back, then your wallet is not compatible."
That is a direct quote from the site.
Also how will I know that the bitcoins I recieved are from them? I got a payment of 0.00954424 from a random address I have in my receive coins tab and I don't know what it's for so it it them?