"There are more than 500,000 words in the English language, but a person who masters only 250 words will recognize more than two-thirds of all words shown in television captions—provided the 250 words are those that are most frequently used. Equally dramatic, a beginning reader could be taught just 10 words—the, you, to, a, I, and, of, in, it, that—and then recognize more than one out of every five words. Mastery of the top 79 words means being able to read half of all words captioned." Source: Perspectives in Education and Deafness, Volume 16, Number 1, September/October 1997

What if we were to apply that same concept to learning sign language? 
Design lessons based on accelerated language acquisition techniques that make use of "word frequency" research. Introduce content via a balance between "functions" (what you want to do or accomplish) and "language frequency" (what you most often say to others to accomplish those functions).