what's the best thing i can do for my lats with only dumb bells?

Answer 1

Oh man, you can do all kinds of exercises with dumb bells. They are better than barbells on the whole.

Lean one knee and an arm for support on a small bench while keeping your spine horizontal.
Then with the free arm row the dumbell up, with the arm close to the body, rather than extended to the side at the end which would be stressing the rear deltoid instead.

This is THE lat mass builder for pro body builders. Der Arnold and all the rest use it.