Battlemaster looks like a better option for a crossbow user. Straight class Battlemaster could work really well but with your stats picking up Rogue after reaching 5th in level Fighter looks like a good multiclass option. Sneak attack combined with a combat maneuver could be devastating...
What race are you? What do your stats look like? What are you thinking of doing with a Eldritch build? I personally would not multiclass until after 5th level.