The idea of spell elements is to counterbalance spellcasting with variable element pools: E.g. to cast Ether spells you need to get ether.
It works as 5 different mana pools:Ether,Water,Fire,Earth,Air.
Elements can be derived from other stats:e.g.Stamina=Water(spells cost stamina),Life=Earth(spells cost hp), Linked(e.g. decrease in X is replenished by decrease in Y) via traits/passives or exchanged(e.g. skill that exchanges 30% of X to element Y).

Consumption of elements: Each spell has a cost in all elements:
E.g. spellA cost 5 fire, 0 water, 0 air, 1 ether, 0 earth.
Element pools can be replenished by items/potions and regeneration(more with element affinity boosting regen rates of specific elements see http://videogamedesign.wikidot.com/rpg:element-affinity-and-weapon-affinity )