If you want Ribbon armor, you customize with 99x Dark Matter. This is a pain in the ass to get, unless you are willing to spend tons of hours into doing the monster arena capture thing, where you'll get 99x of them. That's enough for ONE character. Ribbon isn't too neccesary for the first dark aeons.

All the dark aeons are optional, but since you say you don't want spoilers, I'm not gonna say where they are unless you tell me how far out in the game you are

Did i post any spoilers, since you warned about it? I'm sorry if i did..