100% sure there's not enough AD.

Atma's can't make up for normal AD items. Stacking attack speed will render your hits really weak, and you chasing your targets all the way across the map.

Dagger isn't a strong item to get early game at all, mainly because you should NEVER need to attack so often that you'll actually need the AS from Dagger. In a lane, you need to be focused on last hitting and survivability, not constant attacks, meaning that Doran's Blade and Doran's Shield are two much stronger starting items.