Hey ryan! Like everyone has said here, first maybe rethink rolling for the first time at such a young age and second absolutely buy a testing kit and check out what you've bought. To be sure that you have any MDxx, you really only the need a Marquis regeant, but you can buy the Simons as well to be absolutely sure you have MDMA rather than MDA (which is still very fun, but it's more neurotoxic). As for harm reduction, this is a preloading/postloading schedule posted by Advanc3d in the mega-supplements through that will greatly help reduce oxidation damage and will also boost your roll.
Preload (1 hour before)
2000mg - Vitamin C
2500mg - Acetyl-L-Carnitine
400mg - Alpha Lipoic Acid
500mg - Green Tea extract
1x - Quercetin
4000mg Piracetam
During
2x 300mg Alpha Lipoic Acid
Post
2x 2000mg Vitamin C
2x 400mg Alpha Lipoic Acid
3x 100mg 5-HTP
1x Green Tea Extract
1x Quercetin
400mg Magnesium
3000mg Piracetam
1500mg GABA
9mg Melatonin
Now, you're doing it for the first time a much lower dosage, so I'd say you could safely cut the dosages here in half and it'd still do wonders for keeping your brain safe. Keep your doses low for the first time. Like others have said here, start with 0.1 and at the MAX end with 0.15, you absolutely don't need to take anymore than that in a single night. The week before you roll and the day of, be sure to eat very vitamin nutritional meals, lots of dark green veggies and fruit to keep your body healthy (also do this for the week after your roll). I've heard that grapefruit juice and a bit of dark chocolate help to increase the potency of the roll as well. As for water and hydration, like someone said it's really easy to overdo when you're rolling and that's just as bad as being dehydrated. I'd just to buy a camelpack, fill it up all the way, and throughout the night just take small sips from it as needed.
For fun stuff, massages and head scratches during a roll always feel mind blowing. So do any kind of lights, vics vapor rub (especially the nasal inhalers), and any shit that is extremely soft like spirit hoods. If you want to embrace the loving, communal aspect of festivals, make yourself some kandi and go find out about plur
Have fun, be safe, and be responsible.
EDIT:
Also! Something no one told me, after you have a great roll for the first time (which you will if your stuff is actually MDMA), for the next three or four weeks after, it will literally be all you can think about. You'll think about how great it was, how you want to go back, and more than anything you'll think about wanting to do it again. Don't roll again for at least two months (everyone says one at the minimum, but really wait the two), the recommended wait time is 3-4 months. For your age though, I'd honestly make rolling (if you end up making a habit out of it) something you do AT THE MOST once-twice a year. Save it for special occasions to keep the magic going and especially to keep your brain healthy.