you also have to get fire boon for ex to be able to get fire affinity. there are over 20 spells for a mage. the game is also meant for you to change vocations. so naturally you should go to Sorcerer next and you will find even more spells. remember just because YOU are at level 40 doesnt mean you cant beat the game at level 25. im at level 68 and am still in my first playthrough but only because i chose to. the game cant give you new skills FOREVER. no game is gonna have enough skills or moves to continously give you new ones till level 100. also its better that you have to work for them. i hate when a game gives me an awesome move 30 mins before the game ends.
assassin is bad ass because you can get an augment from the strider class that lets you climb faster and reduces your stamina burned while climbing, this lets you climb enemies quicker and then use Dirge Gorge (sword ability) continuously till you bring it down. cyclops and golems are no match. the class allows you to switch between weapons so it allows for more strategy when you select skills and it raises your strength fairly quickly as compared to mystic knight. i believe the mystic knight is flawed because you have to connect with the shield for most of its moves to work . so you have no ranged combat. also the sword is fairly slower than the daggers and there are some enemy types that are easily disposed with daggers while the same enemy (because of its speed) is a bigger challenge with a sword
ummm i figured if you make a forgery it wont work. i tried using one and it never allowed me to until i used it at the rest camp near devilsgrove. everywhere else i tried it said "you cannot use this right now"
since you started at level 15 you will be fine but i tried it at lvel 50 and my magik damage was too low to really use it effectively. it still did decent damage but not as bad ass as im sure you will be at level 50 if you stick with that vocation