The only way my life changed when I was diagnosed was that I got paid for the study I had signed up for, which required I have a diagnosis
Still, for about 20% of people, medication simply doesn't help. For them, coaching and therapy (and education about ADHD) is far more useful.
Check out https://chadd.org/ for lots of fantastic resources
https://astralcodexten.substack.com/p/know-your-amphetamines
If you're not familiar with the author, he's an incredibly talented blogger whose day job is as a psychiatrist.
Unfortunately modafinil is almost 10x the price of dex in Australia if you don't have narcolepsy, and the drug that I suspect would benefit me the most (adderall, a mix of dex and meth) is simply illegal.
Vyvanse is the form that works best for me, but the crash can ruin any of my evening plans since I lose all motivation or sometimes just need a nap.
Strattera also works very well for some people and is easy to get.
When I was undermedicated I was literally falling asleep at random, and had basically no emotional response to almost anything. Getting closer to where I should be over the last few months has made a world of difference.