You can get your chips in different monetary denominations. When you hand the dealer your chips, he or she will ask what denomination you want to designate your chips. If you're at a $5 minimum table, you could make them $1 or you could make them $100 (or anywhere in between). Once you've chosen, they'll place a chip on top of the rail, with a marker on top of that to indicate your colored chips' value.[5]

You don’t have to be a mathematical genius to excel at roulette but it makes sense to memorise the sort of odds you’ll receive for different bets. Although it’s unlikely that a croupier will make a mistake and underpay you, if you don’t know the odds of the bet you’ve placed, how are you supposed to correct them? Even if you’re only playing online roulette, it still pays to familiarise yourself with the odds you’ll receive for betting on different sections of the table. That way you’ll be able to calculate the possible return and can adjust your strategy accordingly. If you don’t know the difference between zero and double-zero roulette for instance, you don’t know how to calculate your odds and you’re just guessing. Don’t guess – calculate. We’ll show you how.

Roulette games have minimum bets, which will be posted on a placard at the table.  Minimum bets work differently for inside bets (specific numbers) and outside bets (everything else).  For outside bets, any bet you make has to be at least the table minimum.  Inside bets can usually be as small as you like, as long as the total of all your inside bets is the table minimum.  For example, with a table minimum of $5, you could put $5 on #14, or $1 each on #14, #27, #8/9, #28/29/30, and #19/20/22/23.  Remember that you can bet inside or outside if you like; there's no requirement to bet both on a given spin.
Officially, there are three variations of Roulette that exist, American, European and French Roulette. Players may bet on a single or a range of numbers, colors red or black, odd or even, or high (19–36) or low (1–18) numbers. The winning number is thus determined when the ball drops into one of 36 colored and numbered pockets on the wheel or a zero pocket (American roulette utilizes a double zero).
Even if there isn't a betting limit, and if you have an infinite credit limit, it still doesn't really work, it just doesn't really fail either. If the martingale strategy is continued indefinitely and without regard to betting limits, your bankroll will hit arbitrarily high positive and negative values. The expected value is still negative, but the variation is so high that it your bankroll won't stay either negative or positive.