I find ‘agere’ a confusing verb. Wheelock’s gives about five different definitions for it and in one exercise ‘age, age’ means ‘come! come!’. What’s the best usage?
Thank you.
that depends on what you’re using it for. 
lots of words can mean different things depending on context. this is the case in any language, including english. it’s all about context. 
“lead” or “drive” covers most of its meanings. It really is somewhat of a generic verb, similar to and often translated as “do”. You won’t see it very often in Wheelock’s except for in phrases such as gratias agere and vitam/tempus/aetatem/etc. agere. In gratias agere for example, you could think of it as meaning “to do thanks”; “to give thanks” is a less literal translation refinement. In the phrases where agere takes some amount of time (vita, tempus, etc.) as a direct object, it is usually best to translate as “to lead/pass ______ (e.g. a life, a year)”.
Wheelock’s gives about five different definitions for it and in one exercise ‘age, age’ means ‘come! come!’.
This imperative form is not from the Latin agere but from the Greek equivalent. Latin has adopted the imperative form of the Greek word which explains why the meaning is so different from that of the corresponding Latin form.