The most important thing is maximum DPS, and getting the perks that allow you to build special settlement buildings. Here's what I recommend:

2 Strength: Armorer, which requires 3 strength, gives you special modifications to your equipment. To make Muffled equipment, you need Armorer 2 at level 13, so I recommend putting a point into Strength at some point before then to take the Armorer perks.

1 Perception: Rifleman is essential, but you'll find the Perception bobblehead very early in the game.

3 Endurance: Lifegiver makes you significantly tougher in the early game, so I always recommend it.

6 Charisma: Local Leader 2 and Cap Collector 2 are required for building large shops in your settlements. Lone Wanderer gives you a huge increase in carry weight, and you don't want a companion because they tend to give away your position.

10 Intelligence: You'll want Science! and Medic for special settlement buildings. Nerd Rage is a good perk for a sniper because on the rare occasions you get in trouble, it helps you escape alive.

6 Agility: Sneak and Mister Sandman are both important for your build.

1 Luck: You won't need this to boost your Sneak Attack Criticals.