You mean your character's spell power? It scales mostly with willpower but also increases when you learn more spells from the same magic school.
You gain some attack and willpower during level ups and through items.
How to get skill points?
Level up or proceed with stories. You get a few after completing various events.
where i go to fight monstters to level up
Rats with Asara (only 2 lvls higher than the rat lvl) and arena duels & monsters.
