Well, most would consider it to be not a typical one (a directly serogonergic one like a PEA, tryptamine or acid). Without any experience it can definitely be trippy but weed is also stimulant, sedative and dissociative - basically almost everything in one.
(Oh I don't mean to say that with experience it's not trippy anymore but if you smoke often that super intense effect definitely diminishes).
Oral weed (space cake, hash brownies etc) those can produce a full-on trip. Well, perhaps smoking as well sometimes... still oral cannabis seems like another ballpark.
About your brain development: that is said to continue until around 25 - I don't think people should purposely wait until then, it could be beneficial to do it before then to really learn some things and change your paradigm and hardwire it better. But before your 18th doesn't seem like a good plan for the reasons I mentioned.
Just in case you experience a full trip and get a lot of ego softening you should definitely have an integrated ego to begin with to give you a sort of life-wire to everyday life with your feet on the ground. Don't get me wrong, a view beyond your ego is significant and you can learn from it but it is just as important to take the 18 years of time to try and complete as well as possible that concept you are looking beyond.
Hopefully you get what I mean...
Anyway I think he meant he tried cannabis and nitrous already so your suggestion wouldn't be that useful.
I am curious, will it be in cactus form or synthetic mescaline you have access to? Be aware that in cactus form the preparation needs to be done very well to get a good experience, and extraction is IMO important - I tried to make a concoction but it was a real pain in the ass to remove water without burning the stuff.
If it's synthetic I'd find it a great achievement that a 15-y.o. Dutchman would find that, possibly as one of the first things to take!
Remember that cactus or synthetic will not go bad unless you let fresh cactus die and rot, so you can just wait a little longer.