Without context, we cannot answer your questions. It depends on who the subject is. The first one is not really a sentence, but might be seen in bullet points (like on a performance report of some sort). The subject is “he” or “she”. The second one is a command — the subject, “you”, is understood (as is usually the case in English with the imperative / command form).

It depends on the noun. It does not appear that you have a noun here. If you are talking about one person, for example, you would say he USES physical gestures, if more than one, they USE ......It is not a complete sentence the way it is written here.

I/we use physical gestures effectively. He/she/it uses physical gestures effectively.