Rough Leather

From WikiAOC

Rough Leather is the first leather item you will encounter in the game. It is a vital component in for instance armorsmithing. 20 Rough Leather is needed to complete the first quest for Skinning. No gathering item will be needed, Leather counts as a regular drop. For severe farming you should kill Prey in either resource zone, its faster then grinding regular mobs of low level. The only other viable way of getting this sought resource is to save it when you level up. (as it will drop from many mobs you will encounter.) Saved rough leather do not affect quest completion. Actually to get credit for quest you need to find it in mobs (your friends or auction house cannot help here).

If you are going to grind prey, Purple Lotus Swamp is best, as Rough Leather only drop from lvl. 20-31 or 32 mobs. It may be easier if you can use a bow to hunt the low level mobs as they will not run away when you attack another close to it as prey does. The north west arc of valley before the plague victims in the Wild Lands of Zelata is a great run, starting with diseased bears (21-25)when you come down the hill to brown bears (29-31)as you go up the ravine where the bandit camp is.

Also the entrance to Conal's Valley has wolves lvl 19-21 and a generally better yield than prey. It is said that the wild pigs in Poitain drop well, but constantly chasing them down may time consuming.