extendscript after effects: is there a way to create a simple module to apply effects

Not sure what exactly you want to improve here.

If you look for a very efficient and fast way to create these kinds of these "a little bit more than a basic preset in one click" tools, Automation Blocks is a great solution. Much faster than writing the code manually. See this tutorial series for an example:

Tutorial Highlight Tools

Automation Blocks is currently available as free, public beta until end of July.

function applyfxx(fxx) { 
    var myComp = app.project.activeItem;
    	  var curItem = app.project.activeItem;
	  var selectedLayers = curItem.selectedLayers;
	  var selectedProperties = app.project.activeItem.selectedProperties;
var preCompLayer = myComp.selectedLayers[0];
      if (selectedLayers == 0){
	    alert("Please Select at least one Layer");
        return;
        }

preCompLayer.property("Effects").addProperty(fxx);
}
// on selected layer

	
applyfxx("VC Orb");

maybe you can help fix this?

function applyfxx(fxx,selected layer) { 
var myComp = app.project.activeItem;
var preCompLayer = myComp.selectedLayers[0];
preCompLayer.property("Effects").addProperty(fxx);
}