A rich people is not one who has the most,but one who needs

此处的is加与不加都可以,加上主语是rich people,不加是并列句,只是意思有点区别,在于语法上没有错误
To learn that a rich person is not one who has the most,but is one who needs theleast.
去学知富有的人不是他的财产最多,而是他对生活的要求最少