To unlock gear 2 you must gain 100% mastery on the base form after eating the gomu gomu fruit and you also need a consumable gear 2 item drop which is dropped from the queen bee boss, finally you must gain bounty stars by defeating bosses for example like brain of ctulhu, eater of worlds,skeletron, etc. Then finally you'll have gear 2. You can take a look at Terraria one piece mod wiki for more info.