Anything and everything you need to know about the Gym Leaders.
There are a total of 16 Gym leaders that need to be challenged and defeated in order to reach Battle City, the home to the Indego Platue and the Ultimate Collosseum. However very few people reach Battle City, making it a hotspot for tough trainers, as there are only 5 gyms in Lithos. In each gym there are 3 leaders with 2 catagories of leaders.
There are 2 catagories of Gym leaders, 2 standard Gym Leaders, and 1 final Gym Master - totaling to 3 leaders in each gym.
Each Gym Leader has the Notable trainer catagory and gives a badge after being defeated and can be battled in any order. However, to battle the Gym Masters they must be challenged in order and use the Important trainer catagory. They give you a unique Outfit after completing a sidequest upon defeating them, as well as a Badge as proof of defeat.