If I remember correctly, you need certain skill level AND you need that skill to be higher than other skills to get that ending.. 50 should be enough, but you will also need it be your highest skill.
Noticeboard quests give you 2 renown each. NPC skill events give you 1 renown each. Normal quests should also give you some renown. I think there are other ways too, but renown is pretty hard to get in general.
