I started at 26
But I know that many people these days start younger with all kinds of drugs. I never even used alcohol or weed until 26 because I was afraid it might "change me." I was chronically depressed because the world was full of suffering (tho my family was more optimistic). A family friend, a retired psychiatrist, told me I should try Valium. I laughed at that since even if Valium were indicated for depression, I was consciously choosing to be depressed because I didn't want to be happy while the world was in pain. Looking back, altho my reasoning was a bit silly, I feel I made the right choice to simply cry out my feelings each night until I could figure out something better.
Research shows that developing brains (especially those under age 25) are more likely to become addicted to substances, more likely to be potentially unstable (mental illness often begins showing in early 20's), and more likely to be enchanted by experiences rather than seeking insight.
I personally do not wish to sell legal entheogens to anyone that I know to be under age 21 or living with parents or guardians who would disapprove. But I cannot control what people do nor determine who is telling me the truth about their age etc. I would simply ask you to please consider, for your own sake and that of others, that as a young person, you would very likely gain much more benefit from a disciplined practice of meditation and insight than with entheogen use. Unlike with substance use, the younger you begin to meditate, the better it is for your brain and your chances of awakening in this lifetime.
The only time I would suggest someone consume an entheogen is if they have already done years of meditation without much benefit and they need an extra boost. In that case I would recommend using low doses of ayahuasca (less than 1g of acacia) to massively boost meditation power (similar to lucid dream meditation). Once insight into no-self dawns, the extra boost will likely not be needed anymore.
PsychedelicTimes has an article on the subject. Here's one relevant highlight:
Understanding Potential Risks
Recognizing the benefits of offering teens use of therapeutic psychedelics does not negate the research showing psychedelics may affect the developing brain differently than the mature brain. Studies have shown that adolescent rats exposed to THC have suffered greater residual cognitive deficits than adult rats. Similarly, some cognitive deficits have been found in adolescent MDMA users but not in adult users. These studies show the importance of fully understanding the potential dangers of adolescent psychedelic use before making it available in a therapeutic setting. Adolescents may need to use lower doses, be restricted to certain psychedelics, or have fewer active therapy sessions in order to mitigate these risks. Alternatively, upon further research, it may be found that psychedelic therapy should be delayed until late adolescence or full maturity is achieved by a patient.