You get increases to your stats from investing in the masteries you choose. You also get attribute points to distribute every level. What I want to know is how I should do so.

Does the final base stats after maxing both masteries determine how you should raise your stats? For example, if both masteries do not raise either your strength or intelligence, is there any point in investing anything into them. For example, should the Conjurer, Summoner, Elementalist, or Soothsayer raise strength? If both masteries increase all your attributes, such as choosing both a fighting and casting mastery, is it a good idea to raise Strength, Intelligence, and Dexterity? Does the damage you focus on dealing affect how you should raise them? How much should I invest into Health or Energy? How high should I raise my stats? Should I only raise them high enough to equip gear?

It wil depend on how you play your class, but basically a petmancer or mage/caster should mainly invest in intel with only enough into dex to equip items. For melee/ranged then it's usually 1/1 str/dex.