You get the hongmoon weapon at approximately lv45, around the silverfrost mountain as stated by Grave. You'll have to use the weapons/accessories given by the quest up till that point.
At some point in the story, they will give you the Oathbreaker accs.
They're buffed up so you won't have to worry much after that. For the meantime, just use whatever they give you.
Haven't come across any upgradeable accessories though. Probably needs to be bought or gained somehow.
I could help you with quests and stuffs if you want me too, I just started not long ago too.