We'd need to have a strict definition of "culture" in order to quantify how many there are, and even then it would be pretty impossible. I figure that it's easy enough to assume that there is at least one major nationalistic culture for each country, followed by several regional subcultures.

Culture is the combined behavioral norms, customs, mores, and taboos of a group of people usually connected by geopolitical ties.

And regarding "my culture", I belong to many. But we can assume that you mean to ask me what the best/worst cultural practice is within my country. I'd figure that the best cultural practice is likely the sacred nature of freedom of information, enshrined in the first amendment of the American Constitution. It's so rigorously and zealously protected by American citizens that there's massive outcry any time government agents or citizen groups attempt to rob a person or persons of their freedom of speech/assembly/press/religion. Certainly this protection is not perfect, and the practice is frequently violated in small or large ways, but it's one of the most admirable things about the country.

The <em>worst</em> cultural practice is probably circumcision. It's the ritualized mutilation of newborn genitals, treated as a completely normal and reasonable behavior by most of the country and vanguarded by vague appeals to religious customs despite the fact that circumcision is a Jewish practice (and last time I checked, all of the American Christians who cut their kids' penises don't observe the Sabbath or eat kosher food). It's an utterly abhorrent practice that's philosophically identical to female genital mutilation, and it should absolutely stop as soon as possible.