Keyframe Assistant>Sequence Layers will get you headed in the right direction. It's pretty easy to select all of your layers and apply the opacity keyframes you would like - as long as they're all selected, a change to one will equal a change to all. Then, once you have their opacity animating on, use the sequence layers command to get them sequenced.
Another option is to use an expression to adjust opacity of the clip based on the in point.. That's what I would do. Trim the layers to the time you want between layers appearing, sequence layers, then select all layers, move the CTI to the end of the comp and use Ctrl/Alt + ] to set a new out point for each layer.
Here's the expression:
fr = .5 ; // seconds for fade in fade out
v = Math.min(
linear(time, inPoint, inPoint + fr, 0, 100))