From level 1-30 you need your stats in intelligence.
After class change, you need 17 in Constitution, 17 in dexterity and the rest in intelligence up to 100. After that, you can distribute how you see fit and restore any points you used but want back at Crean. Use STAT Restoration, not class reset.
and if you decide to reset your class and try out elementalist class, use a Skill reset card from the item mall. (costs Ap).
If you use crean, your class will be resetted, but your skill points will not reset, but disappear