Basically as far as best armour goes, most of it can be found in the final area. Gems are more important, depending on builds, Shulk, Dunban, and seven are the ones who make the most of agility Gems and Attack, Melia and sharla Ether, Reyn aggro, hp, Defence gems. Didn't use Riki much but I would imagine HP, and Ether/Attack gems.