Most cost and time efficient way to sound dampen exterior wall with drywall
Better insulation between the studs helps a lot. You've probably got or your builder is spec'ing fiberglass, which isn't great for sound dampening. Upgrade to mineral wool. Also, a layer of rigid foam or preferably mineral wool on the outside of the wall--covering the plywood or OSB sheathing--will help a lot too.

Better windows also help, if you haven't bought them yet. Triple pane makes a difference vs double-pane.

If everything is already built, then obviously all of those options are fairly disruptive, and increasing the thickness of the drywall on the interior side is a decent approach.