How does stat allocation work in Final Fantasy 14?

You will occasionally receive a stat point when you level up, starting at level 10. At level 50, you will have 30 total bonus points to assign. This amount is always the same for each class that you level, regardless of your class, race and god choices.

You get separate stat points for each class you level up, and assign them to your attributes for that class. So you can put everything in Strength as a Pugilist, then change to a Marauder and put everything in Vitality. When you change to a job associated with that class (ex: Monk for Pugilist, Warrior for Marauder) those stat point allocations carry over, and cannot be changed separately from the base class. This normally isn't a problem, but causes a slight complication for Arcanists since its two jobs, Summoner and Scholar, use two different primary stats (INT and MND, respectively).

If you don't like your stat distribution for a class, you can reset it (freeing all the stat points you've used on that class) by using a Keeper's Hymn, which you can purchase from your Grand Company for 10,000 seals.

With the release of the Stormblood expansion (in Summer 2017), attribute point allocation was removed from the game. (The relevant changes are in the 'Battle System' section of the 4.0 patch notes.) Instead, your primary attribute in any given class or job will increase at an ever-so-slightly faster rate as you level, as if you were applying all of your attribute points there.

As there was nearly no reason to ever assign attribute points to anything other than a job's main stat anyway, this change served to remove a potential source of confusion, streamlining the leveling process a bit. The main outlier, where Summoner and Scholar shared a single attribute point allocation, was also fixed, such that each receives the minor bump to its own appropriate main stat.

Of course, by this point in the game's life, stat scaling has risen to the point where the extra attribute points, were they still around, would account for 1% or less of your total value in that attribute regardless.

All of which to say: It's just not a thing you have to think about anymore.