There is a HUGE amount of words in a single language. It is often overwhelming to a learner and in some cases, deters them from continuing to learn. It is best to start with 100 of the most common words and phrases in a learner's chosen language. These must be practical and have a frequent everyday use. One good way to determine which words to include in a vocabulary like this is for the individual to pay attention to how they speak.
They can distinguish which words they say often and list them down. These words will be the basis of their vocabulary list. It is also helpful to create different sentences using these words for practice. This method is helpful in whittling down what is essential to learn and what is not as important. This allows the learner to spend more time learning more useful phrases and vocabulary that they can make immediate practical use of.