Is there really a starting point that most of us can remember? It's not a drug, but I remember loving to spin around until I was dizzy and couldn't walk. That's probably my first mind altering activity. :)
Caffeine was probably my first drug. I had small sips of coffee before I can remember.
Alcohol was probably next, starting with sips of my dad's beer, and progressing to wine and liquor.
Cannabis was next. Initially smoking flower, later hash. I instantly liked it, more than alcohol. Might have helped that I did cannabis and nitrous oxide for the first time together.
Next was nicotine. It's the one I regret, and the only one I've really felt addicted to.
I stuck with cannabis and alcohol for a while until the opportunity to try mushrooms came up. Had a pretty great time, although I don't find mushrooms something I want to do super frequently. Maybe a few times a year.
Tried cocaine for the first time on my 30th birthday, it was fun. For me it's like turning everything up to 11, without really feeling blurry. It was fun and made me more social. Never had a regular enough supply to get hooked.
Injected morphine once, but my nurse friend blew out my vein and I didn't get the whole experience.
Did Meth a couple years after cocaine. I always describe it as 5 of the best hours of your life followed by 20 of the worst. I can completely understand why people bump again, the come down is not any fun. For me the come down was enough to keep me from seeking it out.
Occasionally I did oral opioids when I had extras around, but I always feel like I'm falling/dying when I take too much, even at well below dangerous levels. Don't ever crave them at all.
Salvia in my mid 30s. Strong, vivid hallucinations, very crazy, but short lived. Again, not something I wanted to do very often.
Crack once, it was like cocaine, but not as cool. Amazing how perception changes the drug experience.
Throughout my life I've abused nicotine, alcohol, and cannabis. Only nicotine became a real addiction. These days I'm mostly a cannabis and alcohol guy, and I'm trending towards more cannabis and less alcohol.