The best strategy for quickly leveling up your characters becomes available once you have reached Gizamaluke’s Grotto in Disc 1. This dungeon has a ladder next to Moguta the Moogle, the one who receives the Kupo Nuts in the Kupo Nut side quest, that you can use to access the Popos Heights.
There are Grand Dragons located in the Popos Heights that yield a ton of experience points when killed. This amount can be further increased if you have fewer party members in your group according to the following:
Therefore, the best strategy to level up one character is to kill off the other characters in your party. This can be further increased by using the 
Level Up ability.
The Grand Dragons themselves can be somewhat difficult to defeat, but with some preparation, the battle can be made much easier. The dragons attack with lightning-based attacks, specifically 
Thundaga, which can be negated by equipping a 
Coral Ring. Other equipment you may want to use would include:
Make use of the Boosters available in the PlayStation 4 version of the game in order to speed up the amount of experience gained (specifically, the High Speed and 9,999 damage Boosters). Use this strategy to quickly level up each of the characters in your main party and to obtain the End of the Road Trophy as described below.
End of the Road
Once one of your characters reaches level 99 you will automatically be rewarded with the The End of the Road Trophy.
