>>1558151Depends on what particularly didn't work for you. In general try recommendations from /int/ DJT or /jp/ DJT.
The rule of thumb is that you need a lot of input, starting as early in the learning process as you can, but the road until you can actually use input effectively is different for everyone.
Some people can just start reading with a dictionary while learning kanji through new learned words. I envy those people, because immersion really is the optimal method if it works for you. I was the other extreme, I had to go through a kanji deck in Anki (Kanjidamage in my case though I ignored their silly mnemonics in favor of my own), Core vocab decks (CorePlus or Core10K), Tae Kim's grammar guides (was good enough for starting out at the time, but now there are better options apparently), and only then I could start reading without endless suffering and migraines. In general, start reading and listening (and writing if that helps you) as soon as possible, usually slightly before you think that you're ready.
ADHD-wise, taking courses or working with a private teacher may help you with accountability and getting some speaking practice, but most of your actual learning and practice will still have to be done on your own, so I guess rely on meds? It's gonna be tough. I don't have a diagnosed ADHD but I have similar enough symptoms and it didn't make the process easy. I don't think there's any trick that works for Japanese in particular that isn't in the generic list of ADHD-related tricks.
But also what
>>1558158 said. I have a few friends who don't care and love Japan regardless, but they found high-paying high skill jobs in foreigner-friendly or foreigner-managed companies. Those who tried working in actual Japanese companies or JET or whatever gave up and came back after a few months or a year. You'll also have to be prepared to live a lonely life because Japanese people are pretty darn racist under all of their outward politeness.