>>20151104Generally, they can be worked through in chronological order (Which this picture displays them in). Go ahead and skim through their debuts to see their slides that talk about their character background, likes and dislikes, tastes in media, and their longterm goals. NijiEN debuts are usually pretty short in the 25-30 minute range each. If you're interested in someone, then you can watch their 2.0 debuts. The 2.0 debuts are usually much better than the originals because the Liver is much less nervous and they will have much more time to explain their passions, from which you can better gauge their personality.
From there, you can check out their schedules and pick a couple of streams that you may be interested in:
https://walfie.github.io/niji-en-pinned/There's absolutely no need to learn about every single one of them. Usually collabs do good enough to introduce you to the rest of the cast.