First off you want high Intelligence. Since your build isn't a combat build (or at least not a good one anyway if you are focusing on steal), you don't need high Action Points, but you do need 8 AG for one of the good steal-type Perks. 8 AG + "Bruiser" trait will get you 7 Action Points.
So, on traits, Bruiser is nice for the extra stat points. Jinxed can be good because if the guy that you just stole from is trying to shoot you, always hope for that critical fail that blows up their weapon or makes them lose their turn as they are trying to chase you.
I don't have a thief character, but I have planned ones, and I like to have high Endurance to make it so that I can survive whoever is shooting at me long enough to run away to the exit grid. Toughness also helps a lot here, because most of the people shooting you will be people with Normal-type weapons.
Perks (not in order):
- Thief
- Master Thief (Only take if you want to put the 50% into Lockpick)
- Harmless (Only take after you get 200+ steal skill)
- Toughness x2
- Awareness (if you have nothing better to put)
- Pickpocket
Tags:
- Steal
- The rest are up to you. If I were to make one I would put Unarmed as a skill because then I would only need 1 Perception. Outdoorsman is good to get around from place to place since you won't be very combative. Lockpick is good if you have 200+ in the skill with Lockpicks to break into Caravans and such.
