To start the Treasure Hunter quests, find your first map at a camp site outside of McFarlane ranch. It will appear randomly inside a chest. After that, use the map and the descriptions below to find the treasure:
go to Vente's Place near Lake Don Julio and easily make your way by the mountains to find this easy treasure.
Head to The Scratching Post, the camp where you meet the soldiers that give you the army uniform. Up the mountains, easy.
Head to Sepulcro graveyard in Mexico, just south of there are a pair of tress, head past them to reach another bunch, search the area.
Head to Casa Madrugada in Mexico, follow the map along the mountains and if you climb on foot on a cliffy part you'll find your treasure.