This is from a 23 year old's perspective (comparing them to 50-60 years old's is just like comparing a 55-60 year old to 85-90 year old's)
Legal age to be in between kid and an adult (meaning that you're neither): 18
The legal age for adulthood to start: 20 (I think that 20 is reasonable, if not then 21)
For Alcohol: 20-22 (20 could actually work out)
For Tobacco: 19-20
For Marijuana: 18-19
For Shrooms (Tobacco is way more harmful, so legalize them): 18-19
To have a job: 14-15 (most are capable of having a job, and they have to start somewhere anyhow)
To drive: 17-18 (not 15-16)
To gamble (in casinos): 18-20
To gamble in the lottery: Why not make it 16-17 if they're working? It would be their cash (and it's not like there'd be any risk of them getting into trouble in stores as they wouldn't be able to purchase Alcohol anyhow).
To live on your own: 16-17 with a parents permission (otherwise 18)
To be able to have a child: While I personally think that it's a bit young to do so, 18. It's their decision anyhow.
To get married: Keep as is, maybe raise it to 20-21?
What should legalization age be on things in your opinion?