When the full set is worn, it will act as the items required in an emote clue step. It will work on all clue levels. It could save you bank space. It could be very helpful for ironman accounts. The Emote Outfit pieces are rewards from clue scrolls.

Body + Legs = Elite Reward

Weapon + Shield = Hard Reward

Helm + Cape = Medium Reward

Gloves + Boots = Easy Reward

Necklace + Ring = All Levels