I need HECA-help. . . Heheheh. . . Oh god pls don't kill me for that

I've been doing. . . alright with the great rainbow unicorn of death. But I can't help but feel like I'm missing out on some of the finer points of perfecting Hecarim. For one, what are some ideal situations in which to use my R? Also, I've been building Stalker's Blade (Warrior), Boots of Swiftness (Furor), Tiamat, Iceborn Gauntlet, and then one or both of Spirit Visage/Trinity Force. Any tips at all, especially detailed ones, are appreciated. I want to perfect him, not just do well.