One-Piece Dress

A One-Piece Dress (One-Piece in the Japanese version) is common Robe-class bodywear available throughout the  Golden Sun series'. It is typically the first and weakest Robe-class bodywear available to the player, and is one of a few pieces of equipment that is limited to female mage-style Adepts.

Basic Description by Game
In all its appearances, a One-Piece Dress increases the wearer's base Defense by 4 points. As a common item, it can be bought repeatedly from Vendors for 25 coins each, and sold for 18 coins each.

In Golden Sun, One-Piece Dresses are sold in Vale, and can be equipped by Mia. In Golden Sun: The Lost Age, they are sold in Daila, and can be equipped by Jenna and Sheba. In Golden Sun: Dark Dawn, they are sold in Carver's Camp, and can be equipped by Karis and Himi.

Analysis
In Golden Sun, a One-Piece Dress is a pointless purchase. At this point, the only Adept that can equip it, Jenna, already has one as part of her beginning equipment setup. Also worth noting is that she will only be in the party a short time, thus, upgrading her equipment to the stronger Travel Vest can be considered a waste of money. Thus, the One Piece Dress will suit her needs at this time. By the time another female Adept, Mia, joins the party, the One Piece Dress will be outclassed by other bodywear.

In Golden Sun: The Lost Age, as in Golden Sun, Jenna starts out in your new party equipped with a One-Piece Dress as part of her beginning equipment setup. It will last her through the prologue, but can be replaced with a stronger Travel Vest once reaching Daila after the main game starts. Since Sheba is equipped with a Travel Vest already, there would obviously be no merit in equipping her with a weaker One-Piece Dress.

In Golden Sun: Dark Dawn, it once again reprises its role as starting gear for females, being Karis's initial armor. Compared to its prior appearances, Karis's One-Piece Dress will remain her bodywear of choice for a longer period of time, as the player will have to complete the beginning dungeon before being allowed to even travel to a town with a Vendor. Additionally, Travel Vests are not available in the first town, Patcher's Place, forcing the player to wait until reaching Carver's Camp before upgrading.