Mystic Common Stat Builds
Full Mag Build
Every two levels:
9 Mag
1 Str
Mystics burn through magic points like crazy. This build will give you the maximum MP and MP recovery to deal with that problem. However, it will also leave you incredibly squishy. This can be partially dealt with by making sure your summons or teammates tank for you and by using the variety of healing skills you gain. Socketing gear with Citrines for HP or Vit stones for HP/defense (starting level 40+), PDef ornaments, and good refines (starting level 90+) are also recommended to counter the problem of low HP.
Vit Build
Every two levels:
7/8 Mag
2/1 Vit
1 Str
If you are someone who is more comfortable with less HP, take 1 Vit point and 8 Mag per 2 levels. Because summons require so much mana, this will give you a helpful advantage. That may make it tough for less experienced players though, because mystics are still pretty squishy and even with 1 Vit per level; a few good hits and they're out.