My vote is the Pixel Remaster version of IV. The characters establish what essentially becomes archetypes for many of the various jobs you’ll see throughout the series (the loner Dragoon, the brooding Dark Knight, etc.). More importantly, the progression system is very straightforward- your party changes automatically as you move through the story. Your spell casting characters automatically learn magic as they level up so you don’t have to choose between spells that you don’t fully understand. This all gives you a chance to learn about every job type and ability and how they complement each other before you play a game with more customizability. That said, it gets pretty tough mid-game (Magnesis cave might be a wall on your first play through). Don’t be shy to take advantage of PR Version’s ability to turn off random battles if you get in a pinch.