At 13 I would say head north on the beach in the commonlands. Almost to the north zone wall. You will find Shin Re' skelletons up there that are group content. You will net yourself about 2-3%xp per fight but will need some solid downtime inbetween. I would stay there until the mobs gray out to you and then maybe head over to the skelletons outside Zarvonn's tower or actually into WC.