Ilum is by far the best place for players to farm up Grade 5 and Grade 6 materials for Scavenging. The amount of materials that are here to be gathered is just simply astounding. Even with multiple people farming here with you, you'll never run out of nodes to gather. Usually I just sporadically run around Ilum and gather nodes while farming Warzones but if you really want to follow a path I found a pretty darn good one to follow (map of it is below). The thing you have to remember with Scavenging is just like Slicing the most nodes you're going to find for this Crew Skill are around camps of Humanoids.
This path was originally made and tested for Archaeology but it seems as if it is useful for more than just farming Archeology nodes. Along this same path I found just as many Slicing, Bioanalysis and Scavenging nodes as I did Archaeology nodes. It is literally like a line of candy, it's just node after node after node and it's a never ending chain. Despite the video being made for Archaeology originally, this video here shows you this exact farming path.
Very few alterations are made in the video depending on if I see a node way off the path (then usually see another, it's like a line of candy...) But the idea is to follow the path a wee bit south, wrap around and follow it way up north into Imperial territory. Everything is friendly to you up here... Aside from the Imperials... Wrap around the western side first then come back down the east.
Once you mesh back down into the first line cut over west and up and go around the circular area far northwest. This is a friendly zone with tons of nodes around it and also a chest you can farm. To read more about this chest and how positively awesome it is click here. Below is a list of all the materials you will be gathering on Ilum with Scavenging. Next to each item is the amount I recieve normally with each farming pass and how much I can sell them for.