Ruby armor is a tier up from Netherite armor. Here's how much protection each armor piece gives:
Ruby Helmet: +5 Armor, +5 Armor Toughness, 611 durability points
Ruby Chestplate: +12 Armor, +5 Armor Toughness, 888 durability points
Ruby Leggings: +9 Armor, +5 Armor Toughness, 833 durability points
Ruby Boots: +3 Armor, +5 Armor Toughness, 722 durability points
All of the pieces of armor come with super fire resistance, giving you massive resistance to being on fire and in lava. In order to craft it, you can look up the recipe in the recipe book!