The Cocktail Dress features a defense rating of 29, and it increases the base PP meter of the Adept by 15 points. It is bought for 4000 coins while its resale value is 3000 coins. This robe can only be equipped by females, so Mia is the only Adept who can wear this in Golden Sun (Jenna and Sheba can equip it in The Lost Age too, though that's a moot point).
This armor is one of the many pieces of equipment that can be won at Tolbi's spring and be used to outfit your party, replacing their outdated equipment acquired beforehand with equipment like this. The Spirit Armor and Kimono are the other bodywear pieces that can be won at the spring. This dress is good by any standard for Mia to wear at that point in the game, being able to increase her PP meter, and the only armors she can wear alternatively by then are the Water Jacket from Kalay for good resistances, and the Kimono, which can provide Mia minor boosts to Agility and Mars Resistance.
It is not strong enough to suffice as a piece of equipment to have in the inventory of the party for when it is transferred into The Lost Age, especially when you consider that the Iris Robe and Mysterious Robe have the much more powerful effects of regenerating a lot of PP every turn.
|Robes in Golden Sun|
|One-Piece Dress • Travel Robe • Silk Robe • China Dress • Jerkin • Cocktail Dress • Blessed Robe • Magical Cassock • Oracle's Robe • Feathered Robe|
|Robes in Golden Sun: The Lost Age|
|Muni Robe • Dragon Robe • Ardagh Robe • Aeolian Cassock • Iris Robe • Mysterious Robe|