Playing roulette gives you a 1:37 (or 1:38) chance of guessing the right number, and the payout is 1:36 (1:37).
Now imagine you could predict the number in 7 of 10 cases, i.e. about 26 times as good as chance! Walk into a casino with 1000$ -heck even 100 or 50 would make you rich pretty damned fast. Just bet 10% of what you came with on whichever number you think ought to come up first. On most days, you will lose 3 times and win 7 times, i.e. you'd reach 2560$ if you started off with 100. (And if I got the payouts right ...)
Of course, you could simply bet half or a third of your winnings on any subsequent bet. Let's go with a third, shall we?
You bet 10$ and earn 360$. Of these, you bet 120$ and get 4320$. (If you lose, just repeat the bet up to two times, or start over with your 10$ from the beginning...). If you win just one more game for 1440$ you get kicked out of the casino 51,840$ richer. After just three bets! (And that's just what you get in the last bet. There's a few thousand bucks in the previous ones, of course. I am too lazy to add those up.)
Now, chances of the first three bets working out at 0.7 each are just over 0.3. So it probably wouldn't be too hard to distribute the bets over a few days and several different casinos to max out your winnings before being banned, right?
I would quit my day jobs if I had odds like that, and Mr Randi and his cheapo challenge would be the least of my worries.