This Seeking Tech guide will show you the best grinding spot for the first world in the Pixel Remaster version of Final Fantasy V.
To begin, make sure you unlock the Control ability from the Beastmaster Job for multiple characters. This will allow you to control your enemies.
I also recommend that you use Boosts so that you can cut down on the grinding time.
Next, you need to travel to a small island located to the southeast of the world map. It is the second island to the left of the crescent shaped island. The earliest you can get to this island is right after you unlock the fire-powered ship as a transportation vehicle.
On this island, you will only encounter the Prototype. To defeat this tough enemy, use the Control ability. This may end up missing, so make sure you have this ability for multiple characters.
Once the Prototype is under your control, have it use the Self-Destruct on itself. This should instantly defeat the enemy.
If you have boosts enabled to the 4x maximum, then you will earn 8000 experience points and 16 ability points per battle.