The First International has been a subject limited by the doctrinaire Marxist treatment of it. I used to think that reading about the First International was about as appealing as eating dried mulch, but there's actually a pretty nifty concept behind it.
What the First International did was connect labor movement activists with socialist theorists so that a kind of mixture was formed that somewhat took concepts of labor possibilities farther than they had been taken previously. It also of course helped coordination and communication between radical labor groups across borders. The benefit was essentially for the workers and in an ideal world the International would not have been dominated by figures like Marx but would instead of taken their ideas, thanked them, and then made decisions on their own. At its best the concept of an international signifies a radical resource for labor or some sort of radical labor formation that explicitly discusses labor issues in relation to greater societal change, and that links up with similar groups in other areas.