Since early Beuritanian age, there were people who had questioned and studied some supernatural phenomena so called magic. As time goes, the knowledge of magic became a well organized study and great mages began to appear. With their knowledge on magic, they could handle the elements of every material in the world, and actually they made the world more flourish. By the way, their study was not used only for peaceful purposes. It also used as the tool for wars. Mages, who have most scary power with their extreme mental ability, however have too weak body to fight melee.
Mages use staffs to cast strong magic spells. They have a lot of MP but lack HP. Just like Priests, Mages have low defence. They get very strong magic attacks at the job change, and at later levels they get MP regeneration, a teleport skill, and a buff that increases the party’s mp temporarily. Elementalists use stronger magic attacks. Summoners summon spirits that increase their stats and then can be used as weapons.
These are merely suggested builds.
You only need to put points into Int and Spr. Str only adds damage if you use the level 7 and below novice weapons. Dex does nothing for Mages. Since mages have a long range and many strong elemental damage skills adding points in only Int is suggested, and only adding points into Spr for extra defense/hp if you feel the need.
The type of build you use will vary depending on what you plan on advancing to for the second job. Mages can become either a Summoner or an Elementalist.
Summoners have skills to guard them so Elementalists might need extra SPR. But generally the builds are the same. Full INT is also an option because Mages are long range.