I just started playing Splatoon 2 and have tried using my Amiibo's in game to unlock the special amiibo gear. However when I use the normal inkling and squid amiibos they only give me one piece of gear, and I am unable to use the Callie and Maria amiibos at all. How exactly do I get the rest of the special amiibo gear sets?
To unlock the special amiibo sets of gear you need to increase your level in Splatoon to level 7 which unlocks you the shirt of the amiibo sets once you use the amiibo again after getting to level 7. To complete the set you need to get to level 10 and use the amiibo again to unlock the shoes.
The Callie and Maria amiibos also include a special requirement for you to beat Octo Valley before you are even able to use them. Once you complete Octo Valley both the Callie and Maria amiibo work the exact same way as the other amiibos.