Leather Armor

A Leather Armor is the first Armor-class bodywear available throughout the Golden Sun series.

Basic Description by Game
Leather Armor increases the wearer's base Defense by 12 points. As a common armor, it can be bought repeatedly from Vendors for 240 coins each, and sold for 180 coins each.

In Golden Sun, Leather Armor is sold by armor vendors in Bilibin, Imil, and Kolima, and can be equipped by Isaac and Garet. In Golden Sun: The Lost Age, Leather Armor is sold in Alhafra and Garoh and equipped by Felix and Piers. In Golden Sun: Dark Dawn, Leather Armor is sold in Harapa and Ayuthay, and can be equipped by Matthew, Eoleo, and Tyrell.

Analysis
In Golden Sun when Leather Armor can first be bought in Bilibin, the strongest body armor Isaac and Garet would be wearing would be Travel Vests, and Leather Armors would be adequate upgrades over the Travel Vests. The defense upgrade here would not be quite as major as if they are equipped with Wooden Shields and they buy the expensive but strong Bronze Shields at Bilibin's vendor to replace those. Since there are also strong weapons to consider buying at Bilibin's vendor and coin reserves are most likely quite limited at that point, it is important to balance out which are the most worthy acquisitions for your money unless many battles outside Bilibin are fought for more coins.

In Golden Sun: The Lost Age, when Leather Armor can first be bought in Alhafra, it might be worth getting the more expensive but much more practical Psynergy Armor that can already be bought for Felix in Mikasalla, so the Leather Armor might not ever see any practical use.

In Golden Sun: Dark Dawn, when Leather Armor first becomes available, it can be useful for a time, as the only better body armor available is the Elven Shirt, which can only be used by one warrior Adept, if it is used by either of them at all. However, the better Adept's Clothes quickly become available once Ayuthay is reached, so the Leather Armor may or may not be considered worth purchasing for the sake of the intervening time.