I am a 3L who is considering getting a PhD since I have been told that you need one to make it in academia. However I am not sure which PhD would be the best to persue, any ideas?

One does not need a PHD to make in as a legal academic. If you want to get one though, I would suggest you focus on getting one in an area in which you are really interested, since it is a great deal of time an effort to commit.