I am looking for the best possible DPS build for a MAGE/PRIEST,
if you have ant suggestions plz message me or post here.Posting here will help other ppl, thanks.

Here's a useful site, I'm looking into this myself because my first mage was M/K wind mage:

http://theromwiki.com/index.php/Mage_Skills

From what I can tell, you'll want to go flame mage with the Priest secondary. Use the TP for the priest for regeneration, quick heal and magic barrier so that your mage isn't quite as squishy.

Your attacks will most likely be Fireball, Flame, and Purgatory Flame. You can experiment with Phoenix, but I don't like it a ton.

I'll post back once I figure out more, lol.

Max:
M/P elite buff
Flame
Fire Knowledge
Lightning (can get long root @ high lvls)
*Wind Knowledge
Rising Tide

30-max:
Fire Ball
Regen
Urgent Heal
Thunder Storm

rest:
any of the passive or self buffs you like

Early on you will only be able to keep 2 skills @ max, with some investment in others. So concentrate on Flame > Fireknowledge > Lightning (find a comfortable timer and leave @ that level till higher).