This video shows you how to farm 10 familiar badges. These are needed to unlock all 3 slots of your familiar system. These are the 10 easiest for me personally. There are some that are equally easy but I didnt farm them. I just happened to get these first. Therefore, it is not to say everything else is hard, except these 10.
How To Unlock 3 Familiar Slots / Gather 10 Badges (Familiar Revamp) MapleStory