Well first you will have to know the cooldowns of your spells as a mage.
For example its not the same if you do UE first or if you do it after. You need to do the best optimized combination of spells depending on the spells cooldown , for example Sorcerer ( Exevo vis hur then exevo gran vis lux , then sd and then UE) thats that's the better combination of spells. But the most important skill as a mage on pvp is the hability ability you have throwing magic walls and paralyne paralyze rune and at the same time the hability ability of predict your enemy moves, if you control all this things you will be a very nice mage on pvp. Hope it helps ! :p