Thank you for your input, gang! :)
Okay, to summarize, here are the list of things that might help when you are unable to get medicated or therapy:
1. Supplements: Omega-3, Zinc, Lithium (has severe side effects, but it works)
2. Mindfulness: Meditation/Yoga
3. Routines (according to HN answers)
Here is the list of things that I personally (!) think that might help:
4. Digital organization: Johnny File System, PARA Method
Here is the list of things I am personally (!) unsure about:
5. Offline organization/planning: Bullet Journaling
6. General organization: minimalism? Decluttering?
The list of things that need also attention:
7. Social skills & interpreting social cues correctly
8. Interpersonal skills & soft skills (manners?)
9. Effective "crutches" for things like impulsivity
Some more ideas that might help or not - these are rather experimental:
10. Fasting (for mood improvement?): https://www.hal.inserm.fr/file/index/docid/789122/filename/F...
And remember: use your own brain first don't trust anyone so easily! :)
(Except your therapist/doctor, if you have access to one.)
Final note: we need a Scott Meyers type of book for "Effective ADHD".