OK those are enough tips if I may say so.
All the right stuff has been said. Mostly: don't take a drug at a concert or party for the first time. About drugs (psychedelics) you do know I want to add that you should be able to tell yourself how it would be at a party but do not underestimate the different setting!!
Ketamine and methoxetamine could be taken as a party drug but they are definitely less accessible than drugs like empathogens / ecstacy like drugs.
With dissociatives: even if you know the drug, lower the dose significantly - but also first get to know it at home. The same goes for psychedelics really, but they are more mentally debilitating than physically. Well methoxetamine may not be that debilitating. It got me pretty dizzy though.
Please search for other tripping at concert threads to continue there and stay on the subject. Otherwise create one but I would be surprised if there really aren't any yet, and be like j'accuse, UTFSE on your ass.