I don't think there is a real build at the stage you are in. Most builds require you to have certain skills that are acquired later in the game.
Skills that are good later in the game are:
Worstel's Worry (WW) - good vs bosses and wurms
Conjure Phantasm (CP) - good early in the game
Clumsyness - good vs warriors and rangers
Empathy - good vs warriors and rangers
Any type of disruption - good vs spellcasters (especially vs monks)
Cry of Frustration - good vs all
I don't know what your 2nd profession is so I can't help you to incorporate that into your character.
Every quest is actually easy until you hit Thunderhead keep.
You should be able to have lots of fun with mesmer.
The only thing I can truly help you with is the Ascention quest (in the desert).
Bring the following to it and you will have no problems at all:
Empathy (domination) - Max
Illusion of Weakness (Illusion) - left over
Spirit Shackles (Inspiration) - Max next
Spirit Of Failure (Inspiration)
Signet Of Capture
Res Signet
The last two can be any of the following combinations:
Signet of Capture x2 (for a total of 2 or 3)
Reversal of Fortune
Blindindg Flash
Iron Mist
Light of Dwayna
Resurrect
Dark Fury
Defile Flesh
Enfeebling Blood
Insideous Parasite
Spirit Of Failure
Soul Feast
Any pet skill (except for edge of extinction, energising winds, fertile seasons, primary echo, symbiosis)
Dodge
Lightning Reflexes
Any Axe, Sword, or Hammer skill (just don't go into melee range)
Shields Up
Deflect Arrows
Disciplined Stance
Frenzy
Flury
Basically, any other skill that doesn't do the doppleganger any advantage. Just cast the above spells (the main ones) and watch your foe die.
Remember, do not attack, just cast. Then you will have 100% success in your ascention.
Enjoy