With regard to skills Of Magacian, you should put all the skill(Metin2 gold) points into Mental Strike when you make the job advancement at level 15. Using a staff in lower levels as mentioned maximize damage, because you will die fast if you do not firstly kill them. With greens and full int and good buffs, you can whack off 2K a hit easily with SF, and this is without elements.
Even if you are going Metin2 Psykeeper, use elements when you obtain them. You should max Mental Strike on condition that you are going elementer. Do not sweat it, you gain plenty of skill points. Do not bother even getting the elemental skills until level 30, because that is when you will make an important choice, and even a level 10 first tier elemental skill is much weaker than a level 20 Mental Strike, and you do not want to waste skill points, so level 10 is even too high.
There is quite a few mobs are weak to water and fire from level 30-60. Anyways, you should kill monsters 5 levels over using this tactic. Even on mobs that are neutral element it will still do more damage than the element strong against them. Therefore, get the minimum required spell levels for the two skill's prerequisites and max the final 'tier' After level 60, it changes again. By the way, if you want to max Blinkpool, it is a nice warp skill, and with only 2 elements maxed. You can max it too. You can be likely to max the second to last earth tier too, and forget about rooting. Then you can use the reskill you got from job change. Thanks for reading.