I guess I'm gonna take the other stance on this one. I don't believe that it's necessary to take other drugs to take DMT. They really don't have much to do with each other. DMT's not like most other drug experiences (including the low-dose long-term psychedelic ones that most people who have moderate experience with drugs tend to have). I've administered DMT to people who haven't touched anything else before, and it's gone great each time. I don't personally believe it's a pre-requisite. It's short-acting, so if things do go sour, it won't be for long, and I personally find IME DMT to be more forgiving and embracing than other drugs/psychedelics.

A little late to the party, but I thought I'd share my personal experience. I hugely bit off on the DARE program when I was young. I value my intelligence and was terrified that any type of drug experience would impair that. Still, like you, I was curious about the brain, about consciousness, about life. What I slowly learned is exactly what elphologist1 said: psychedelics are nothing like depressants or stimulants. Growing my own cannabis was my introduction to the life cycle of a plant and started my obsession with plants (which now manifests itself in the form of a vegetable garden). I saw I could grow my own mushrooms and learned a bit about mycology. My first trip changed my life. It gave me a new appreciation on the wonder of the world. I still have no desire to try drugs like cocaine or heroin, but I have a hard time imagining my life without psychedelics. And I don't think I wrecked my brain like Nancy Reagan said I would: I just finished my second degree with honors.

I am curious if you could share that Sam Harris video? I've never seen him talk about psychedelics. Also, are you familiar with Daniel Dennet? He and Harris sit on opposite sides of the free will debate. I don't agree with all of Dennet's points, but in Freedom Evolves he makes a great argument for seeing Conway's Game of Life as a model for consciousness.