Knowing at least a few phrases in sign language is always useful and there are few videos that are a more popular means of learning it than the Sign with Robert series. Giphy has teamed up with Sign with Robert to put together a ton of animated GIFs to help you learn a variety of phrases.
In over 2000 animated GIFs, you can learn various expressions, emotion phrases, lifestyle phrases, and more. Each animated GIF is coupled with the phrase you're learning, which has been reviewed by the Sign with Robert team for accuracy.
This certainly isn't enough to learn sign language on its own, but each of these GIFs works something like an animated flash card that can teach you a few things through repetition. You can find the whole collection over on Giphy's Sign with Robert landing page.