When you become a mage you have to know that you have new statistics, like winsdow and inteligence.
You'll also have a new bar, your mana. You can increase your mana with the inteligence, and when you have more winsdow you can do better hits with mage.
There are quests that gives to you the new parts of armor (cuisses and cuirass) for lvls 11. If you have valor, you can directly buy blue ones from arsenal.
Now you have to know that the monsters and instances for mages are more difficult, because all these new monsters also got magic, and you have to study them to kill them easily.
I recomend you get champion rank before be a mage, because you can buy better spells in the arsenal if you're a champion (if not, in the square of fire, in tower of war mages). After you joined to one school, you can learn different spells, which you'll use later.
There are 2 types of magic, one is like a 'hit', and another like a 'poison'. The poisons does less damage and use more mana, but it's very good when you're like 8vs1, sometimes you kill him and you get scalp
As new monsters and instances, now you got new reputations, new curses (destructors) and many things, so you must pay attention on that. Also in fights, you should be checking all the times your mana, because if you don't have more mana, you have to hit with your weapons. In the tower of war mages, you can buy elixires and scrolls that restores you mana in fight, it's exactly the same as life points, not much myterium there
Then as I said, you have to be studing the different objetives that you go for, but in really, it is not very difficult, only be a concentrated in your objetives.
Also, you'll notice that you hit very hard now
You fell god