you only NEED one character to do everything you need in the game, like i said you can play all the different jobs on one character, only reason you will need an additional character is if you want additional storage(like to store sets of armor) or if your main character isnt a good race for a job you want to play (i.e. one of my characters is a 75BLM, which is a tarutaru for higher INT and MND, and my other character is a 75DRG, which is elvaan for higher STR and MND)