My therapist referred me to a neuro-psychologist who tested me over two days. I didn’t pay for it, but I know similar tests are around $2k, because my friend did something similar. You should know there’s different ways to test for it, I didn’t do the eye tracking computerized test.
Meds are going to depend on your brain and body. I take Vyvanse and it lasts about 4 hours, which is when I’ll take an Adderall IR booster if I need longer focus in a day. Expense is actually less of an issue than being able to reliably fill them, if you’re in the states. Lots of shortages, and an annoying 28 day personal limit. I’ve gone weeks without because I kept forgetting to request a refill lol
Edit: for what it’s worth, you’ll likely need to be able to point to this being a lifelong issue and not a newly developed one. And they might not offer stimulants right away if you’re diagnosed. Lots of people get by on Strattera or Wellbutrin
Just tagging on for your post-it note thing: I’ve found out absurdly helpful to put post-it flags (they’re actually called that lol) in places my adhd strikes hardest so I at least have a visual reminder something needs to be done. I have a couple on my TV, and even though I haven’t actually used the TV in months, it’s in a good location for that my eyes wander to. Alarms and notifications are easy for me to ignore/mute or get annoyed by, the flags are inoffensive and passive