is it should be mixed between shooting , Vigor and toughness ?
As rice has already stated, Aim and Dodge are the most important skills.
Next most important is Vigor OR Shooting (not both). If you have a melee weapon you need Vigor, if you have a ranged weapon you need Shooting.
For an attacker:
To hit: Aim, plus a little bit of appearance if greater than opponent tactics
To dodge: Dodge
To increase damage to opponent: Vigor (for melee), Shooting (for ranged)
To reduce damage to you: Toughness (against melee), Reflexes (against ranged)
For a defender (clothes you wear when working or travelling) you don't know whether your opponent is melee or ranged, so you need:
To hit: Aim
To dodge: Dodge, plus a little bit of tacticsif greater than opponent appearance
To increase damage to opponent: Vigor (for melee), Shooting (for ranged)
To reduce damage to you: Toughness or Relexes, but you won't know which
(Disclaimer, I'm specced as a fort fighter. I think this is all correct, but if anything is wrong a dueller will correct me)