PVP Jest build
 

This build is from my OWN experience. You may wish to follow it, use it as a reference, or just ignore it.

Starting as a Theif
Focus on Hero quest (red ! on map) and complete them.
Go out, fight a few mobs and get to level 2 and learn ariel frenzy. Or you can just rush in MM.
Remember to get any quest from sign post if available before going in MM.

Theif SkillBuild
Your main attacks will be Launch -> Frenzy -> Launch -> Frenzy
Launch : 5
Ariel Frenzy : 5
Cut-down : 1
Con : 1
Dex : 5 (For accuracy and critical rating) *High MP usage
Rocket Punch : 5 (to keep combo running)
Nozzle Tuning : 5
You can pump the rest however you like, Since you'll be getting a skill reset scroll upon advancement.

Training 1-20
1-6 : Vegabond
6-11 : Vega
11-16 : Tutu
16-20 : Toto

Jester
Combo-ing is going to be much easier now, as well as killing.

Skill Build
Since you will receive a a skill reset scroll, use it!
Launch : 1
Ariel Frenzy : 5
Cut Down : 2
Rocket Punch : 5
Nozzle Tuning : 5
Exit : 1
Burrow : 5 (I am a burrow and attack jest)
Claw mastery : 5
Rolling sting : 1
Final decision : 5
Uppercut : 5
ESP : 5 (Change if you like)
Motion Cap: 5

Your attacking combo will be something like this : Final Decision, UpperCut, Frenzy.
Attacking style :
1) Jump in, Cut-down
2) Burrow up and F-Decision

Training Place
Continue Hero quest!
20-25 : Hookah
25-31 : Alvida
31-36 : Atria / Chaos East MM
36-40 : Lord of Night / Chaos White bearded
*LoN not advisable due to maze-like maps and little mobs

That's all. First time writing guide, I know it sucks.
Timing and practice is very important in PvP. Good luck.