Don't bother with DXM... shit is destructive. I had some problems with it when I was like 16. I wound up tripping on the stuff like literally every day for months at a time. Fucked me completely up for about two years and I'm still not completely right. My mind is noticeably slower, first of all. I burned a lot of bridges and even wound up dropping out of high school as an indirect result of my obsession with tripping. I've developed problems concentrating, experienced weight gain during and the few months after, developed numerous stomach and sleeping related issues, etc.
Most of the damage done has been reversed after about 2 years of sobriety, but still. It was two years of bullshit, losing the roughly 40 lbs I gained, experiencing depression, and just in general fucking up my life. Back on track, in college etc now..
Also, IF you're going to do it... stay away from Mucinex bro. It has another ingredient in it other than DXM (I forget the name atm, starts with a 'G') that is designed to prevent you from abusing it. The whole purpose is to make you puke if you try to take too much if I remember correctly. The safest methods IMO are the Robitussin Gel Caps that just have pure DXM in them. You could also chug a bottle of syrup, but be sure to check the ingredients. Also, be sure to calculate out how much DXM you're doing if you decide to just drink the syrup. At my peak I could've easily handled like 600-700mg, but your tolerance is most likely different.
edit:
In support of the above poster, I would say after experiencing 2ce it is clearly the better drug. I have no idea on the health risks and whatnot, but if you just want a recreation drug that you do maybe once or twice a month, 2ce is FAR more enjoyable. Never in my entire experience with DXM did I have a closed eye hallucination, much less an open eye one. Within a few minutes of doing my bump of 2ce I was literally soaring through the universe. This one experience alone has ignited a passion for the universe within me. Afterwards, I found myself watching the sunrise while laying out in my front lawn like a dumbass... but an enlightened dumbass at least. Truly revolutionary for the mind IMO.. on DXM I just sat there in a daze.. Fucking stupid looking back on it. Dissociatives are only fun until you experience something better, then you realize you were really having a shitty time all along.