Layer Collision

I have a 2d-game I'm working on right now. Unfortunately, I don't know enough about layer masking and collision to set up a few things. I'm trying to make it so a punch effect won't collide with my player or itself, if that makes any sense. It's a Smash Bros-esque style game, but I can't get the punching to work as they won't spawn unless the area is clear, which eliminates the possibility of punching someone. Anyone think they can help?