Why good feng shui comes in three?

Someone told me that good feng shui comes in three. I have two lucky bamboo and two is bad. They said I should go get another lucky bamboo to make it three because three is good feng shui. Why does good feng shui comes in there?
The number three in traditional Feng Shui is considered to be auspicious because it means/symbolizes creation/renewal. You'll notice that many Feng Shui enhancers and remedies come in the form of threes and with good reasoning.
You'll notice three coins tied with a red ribbon which is used for the creation of wealth (the coins are considered to boost wealth). The Fu Lu Shou (aka Three Star Gods) who create harmony and three blessings into your home. The list goes on of many auspicious entities or events in history that involve the number three.
There are other lucky numbers in Feng Shui though, the most famous one being 8 (prosperity) and 9 (longevity).

understanding fengshui isn't really that easy. you need to know why is the bamboo for in the first place.
the numbers 3 and 4 are not lucky numbers. but each of these numbers become lucky when each one of them combine with certain numbers. because these numbers present the element wood. thus, using 3 bamboos is just like having 2 wood elements in that area (1. for having bamboo, 2. for the 3 units of bamboo).
but i like to emphasize for you to use number 4 or having 4 green plants or bamboo. because the number 4 when combined with 1 signifies love or education; and when combine with 9 it forms the celebration of life/ family.
on the other hand, the number 3 always signifies conflict, even when the combination is good; while number 2 signifies illness
so having 4 green plants is like having triple wood element, because:
1). 4 units = wood
2). being green = wood
3). plant itself = wood
since you are watering it everyday. water is 1. thus, you get 4 and 1, which is a good combination.
in 2008, it is best to place 9 green plants at the east most and southeast most parts of the house, for you to attract new people into you life. this also means that you attract potential customers into your business. do not put the plants if the area is a toilet or a bedroom. and remove them when some people bothers you.