Someone recently asked this, and there’s no short answer, really; and it’s not just about what you take. But for what it’s worth, here goes:
I have ADHD and I am no longer able to take methylphenidate (typical tradenames: Ritalin, Concerta). Also, ADHD used to have a fantastic wonderful spontaneous and hyperactive fun side for me, but that has now turned to lethargic sludge.
Besides a low carbohydrate diet, some of the most important things for me are Vitamin D (I was extremely deficient a year ago, in spite of daily supplementation) and B vitamins — especially biotin, folate (not folic acid) and methylcobalamin. Phosphatidylcholine is essential for me, and so is taurine. These things keep me employed. Obviously, I do try to get them in through diet too.
I take quite an expensive Omega 3 supplement which my doctor insists on for improving membrane health in the long term.
Sometimes I also take acetyl-l-carnitine (essential also for depression, although I don’t have that) and phosphatidylserine.
These are all typical deficiencies in many people with ADHD.
I’m postmenopausal and I have an oestrogen deficiency for which I get treatment, and I am mildly intolerant to salicylates/phenols — that’s also typical in some cases of ADHD.
I also try to drink more coffee. I realise that people with too much cortisol may need to take caffeine in combination with theanine for a less jittery effect, but I don’t have high cortisol.
Magnesium is super important for sleep, sensory issues and a bunch of other things. Because of poor gut health, I become deficient quite quickly, so I regularly supplement with magnesium glycinate and also do several things to improve intestinal absorption.
Phosphatidylcholine is actually one of my favourite things, but it’s obviously not just a one-step fix. ADHD is an umbrella term for a variety of things and several of the abovementioned measures may or may not be relevant in your case.