For this trick, you’ll need to meet the following requirements:
* You have already reached Ionis (since the consumables needed are found in the item shop there)
* Contraband Super Specialty (Specialties: Pickpocketing, Replication)
* One character with maxed out Replication (Skill: Imitation)
To fully take advantage of this trick and to make it easier to pull off, it will also help to have the following:
* Magic Camera (support item for Replication, buy from Ionis item shop)
* Ririca (superior magic camera, crafted via Machinist Specialty)
* Orchestra Super Specialty or Goddess’ Arrival song (Music Specialty)
Using the Super Specialty Skill Contraband, buy a full stock of Premium Papers (from the Ionis item shop) and keep forging materials until you get at least one Counterfeit Medal. The higher the Contraband level, the better chances of producing this item. Further boost your chances by having Orchestra Super Specialty or Goddess’ Arrival songs playing in the background.
When used on a character, the Counterfeit Medal will reduce the character’s required EXP to 1. Since it is really hard to produce, Replicating it is the only viable solution. You'll need a Magic Camera and some Magic Films to attempt to reproduce it. It is advisable to have a maxed out Imitation skill before attempting. Try to create a Ririca camera through Machinery Specialty to increase your replication chances dramatically! You can even sell various Forged items that you'll get using this Super Specialty for good amounts of money.
Keep replicating the Counterfeit Medal until you have 20. Now head outside the city and fight random battles. If you have someone with the Scout Specialty unlocked, you can even set the team to Look for Enemies to increase your encounter rate. After leveling up, use the Counterfeit Medal once again to bring down the required EXP to 1 and repeat the process.
Just make sure to leave at least 1 Counterfeit Medal at all times so you don’t have to produce it again. Replicate that Counterfeit Medal and use them as much as you want. Take note that you can only use this trick up to LV99. While the game’s level cap is LV255, you can finish the main story with characters around the LV60+ range.