SHROOMS, though not addictive and you cannot do them too often or you'll build up a resistance, but they're awesome! you see trippy shit (pretty much whatever your brain can render, and believe me, it can render alot), laugh uncontrollably, have epiphanies, and really stranger body sensations (you'll be walking, but feel like you're falling out of a plane). but you can also have bad trips and see scary shit, or contemplate death, or think about god and freak yourself out. lots of fun though!
alternatively you can watch Requiem for a Dream (2000), if you're going for something darker. its got some of the themes you're writing about in it, its a bit graphic though.