Honestly? The fastest way to lock in Sneak Attacks would be just to take 1 level of Snakebite Brawler and Gangup. You are your own ally so as long as one other person is adjacent to the enemy, you get sneak attack.
You count as your own ally. Unless otherwise stated or if doing so would make no sense or be impossible.
Gang Up is quite obviously meant to be used with two other allies, and as such this would be a case when the Own Ally FAQ doesn't apply.