Dragonslayer as a Mentor (SR5, Page 321-322) and take "Increased Accuracy (Gunnery)" or Wise Warrior and have "Improve Ability (Gunnery)".
The Artisan's Way from Street Grimoire (Page 176.). It might as well be named "The Way Of The Wheelman".
Rigger 5.0, just, yes, all of it.