In Texas Hold 'em, having 2 and 7 off suits is rated the worst hand. This is because they're the two lowest cards you can have, and they can't create a straight (there are five cards between 2 and 7). Even if they're suited, they'll give you a low flush, and if they both create pairs, it'll be a poor hand.

The royal flush is a case of the straight flush. It can be formed 4 ways (one for each suit), giving it a probability of 0.000154% and odds of 649,739 : 1.

To make money playing roulette, correctly guess the number or type of number the ball will land on when the dealer spins the wheel. In a roulette round, play starts after the dealer clears the table of the previous game. At this time, place your bets on your desired number slots.

Seriously: roulette is random, every number has equal chance of winning. From pure probability theory you can calculate what is the probability of winning, no luck involved. I define "luck" as the difference between average expected results to actual results. In the long run it's zero.