Hi there, I also have ADHD! I have taken MDMA before my diagnosis pre-meds, and again while on methylphenidate (Ritalin/Concerta) and amphetamines (Adderall & Vyvanse).
From my personal experiences, having ADHD does not really affect your roll... except maybe that maybe your ADHD mind can take away creative and inspiring experiences that will be completely unique to you.
By doing some online research for drug interactions with your meds beforehand, that will pretty much tell you what you need to know. I HIGHLY recommend not taking your meds before and after a roll. Stopping your meds is no big deal for ADHD stimulants, since they do not stay in your system for long and are not required to be taken everyday to be effective. (Antidepressants are a different story, and should be approached with much more caution.) I try not to take amphetamines the day before or after rolling. Two or more days before and after is even better, especially for the first time, where the come-up and come-down will feel strange to you. I have been on different doses of different meds and have had no negative side effects by following this rule. However, I'm no expert... please do your own research until you feel that you understand and are completely comfortable with what you have read. Each med and dose is different for each person.
If you're specifically concerned about dosage, set your limit and stick to it! Less is always more, for everyone and not just ADHDers. A normal low dose is perfect. It is quite common to see your friends coming-up and peaking and feeling like yours didn't work yet... but trust me... it will work. I think it's probably an ADHD tendency to want to do more to get the MDMA to kick in faster, but that's a bad idea. If you have impulsivity symptoms, do not take more than you planned even if you want to. Waiting an extra hour (or sometimes just 5 minutes that feels like an hour!) is soooooo worth it. Doing too much leads to no fun and potentially bad health problems.
ADHD can make us be impulsive and take risks at times, but MDMA is not a substance to be toyed with. Take it - it's beautiful! - but always plan your dose and test your pills, even if you generally like to live on the wild side.