"Fast paced and freaky" is an understatement. I'd say if you're prepared for the most intense experiences of the emotional spectrum, both bad and good, then you're about 1/2 way prepared
Psychedelics unlike dissociatives like DXM don't really come with the "fuzzy blanket" effect of having no cares in the world and just feeling amazingly blissful, they depend very much on your mindstate at the time - if you're feeling good you'll be blissful and full of awe, if things are getting you down it can be quite a scary experience.
It's important to be prepared, DMT, DXM and Weed are very different drugs, if you've tried doses of 800mg+ DXM you're getting into the sort of intensity of DMT, albeit with dissociatives it's more emotionally bland - just pure trippyness and euphoria, while with DMT be prepared to have all of your senses bombarded like never before.
One thing's for certain, don't go combining it with booze, or even weed, especially your first time, it can really turn a DMT trip rather chaotic and ruin the experience.
Another thing I'd say is I don't think DMT at 15 could be a rewarding experience really, of course everyone is different, but while I've gained a lot from psychedelics, I'm currently 19, first tried DMT two months ago, and I know I'm nowhere near ready for it at this age.
But most importantly, I really wouldn't smoke DMT in a party environment, that's probably the worst setting I could think of for DMT. Go somewhere quiet with someone to take the pipe off you when you take the hit, as you won't recognise your body or the pipe if you can even see them once you break through. Make sure you're in a good state of mind beforehand, let go of all expectations, and see what happens. Like I said though, I wouldn't even remotely consider it for a few years at least, DMT is really not something to have as your first psychedelic experience at 15.