Ok ,I dont always master a spell before moving on..When you level and new spells are available I have found there can be a new more powerful spell available in your element and I will learn it as soon as possible then sometimes when I level there is not a new spell for my particular chosen element so I will "Improve it" then. I also have inactivated all my lower level spells in order to use only my highhest spells so when duelling your using your best weapons....Never take a knife to a gunfight...especially when attacking higher to gain exp points