Get yourself a direwolf. I dont know why metal hatchet is rated highest for gathering. Direwolf absolutely destroys for pelt. Gathered 4k pelt in +- 10 minutes. Have 2 ascendant armour pieces already. Target rhinos mainly.
On the island, run to the attic with an argent, kill a bunch of things, (direwolf, meglarcos, etc,) and then hop off and harvest it really fast. Then, hop back on your argh and put all the hide in there, since it has a ton of weight. At the end of day, you could come home with thousands.