I liked the dwarven ruin you go to with Neloth, the outside construction looks cool, as for the inside, first time I've seen any magic from the dwarves it was amazing (Those cube things that open doors).
I like Miiraks robes, I use the robes,boots and blades sword and he looks like a robed samurai.
I have to start a new save now because I played the storyline for the first time, and properly traveled the island ( I was on the dawnguard dlc too much) and wanted to try a few different builds like mage with the story, Should have made a perma save at "Horn of jurgen windcaller"
Don't know what heartstones are used for, though in the game people use them for ressurecting others?