I'll have more to add when I'm not on my phone, but something to be prepared for is that just because a dxm product doesn't contain any other active ingredients such as guafinesin or cpm, doesn't mean that nausea won't occur. among people i know, it's a common misconception that dxm-only robotussin syrup and gelcaps won't make you sick. i had a few dxm experiences years back but they were with coricidin pills and as you probably know that's dangerous. recently i tried again using the 3mg/ml robotussin syrup with nothing else in it, and one bottle (118ml) had me feeling wonderful with no nausea. it was a pretty good dissociative experience. my girlfriend did the same with me and was so nauseous she was crying with her head in the toilet for 5 hours. the next time i used dxm since then, with the same syrup, the nausea was agonizing and i couldn't throw up. it's different for everyone, probably depends on diet, your overall health, any other drugs/medications you're on. i was coming down from taking vyvanse and i hadn't eaten and maybe that was the problem.
edit: Try to make sure to stay in one place alone, and if anyone is going to see you, make it be someone who knows you're tripping because it will be very obvious and your movements/mannerisms will creep them out. I just do it in my room alone or with my girlfriend with only a dim lamp and my computer on. My favorite thing to do on DXM that I recommend is to sit in bed, grab my laptop and speakers/headphones, and just listen to music with the lights dimmed/off. Personal taste, but when the DXM comes on, I'd say you should listen to some shoegaze music. MXE/DXM and Slowdive really go hand in hand. Or any music that you'd prefer, I could never describe how epic, dreamy, euphoric, and intensified music is on a good trip.
I'm 19 as well and dissociatives always seem to take me to areas of my brain, memories, ways of perceiving things, etc. from when I was younger. I always end up at this singularity, like a grand realization about my life currently, based on the memories DXM takes me to that I've forgotten for a long time. What might surprise you, though, will be the memories you're taken to that have been buried deep in your head but that are more recent. If your intention is to revisit childhood memories that are kind of blurred and hard to remember now, I think it'll happen. It's like at really high DXM doses, during the introspective part of the trip, you're navigating and exploring inside your own brain and nowhere is off-limits. There's also, for me, a part of the trip where I'm not hallucinating but I'm vividly imagining places in my mind almost as if I were seeing them. Not sure if it's just subjective to me or if it's a common thing, but I envision smoothly and slowly flying over strange landscapes that are animated in a shitty 80s-90s kind of way, basically like a vaporwave video. Something like this
http://www.youtube.com/watch?v=y3L3...RDcwi_JnkMuU fZH9VbgAS&feature=share&index=84
During most of my dissociative experiences, I've had a short, ~30 minute period that's like a "bad trip" i guess, but it's not that bad. I look forward to it. It's like your view of everything suddenly becomes darker, people's lives and the world just seem scary and confusing. I thought my friend who was texting me had developed schizophrenia. It's probably how a baby would see the world if they were exposed to the complete reality that you start to see when you become an adult. That part of the trip is always where I come out having made some epic realization. Don't worry, if you're doing this prepared in an appropriate setting, you'll be in good hands.
If you don't enjoy the trip, try finding some MXE. I've had a couple of incredible times with it and never gotten sick or anything. I prefer it over DXM.
