The real issue with Adult ADHD is you are expected to manage it yourself... Gee thanks why not make my life as hard as possible...
But that said, I would say the baseline for support is a Psychiatrist or PMHNP-BC - Psychiatric Nurse Practitioner. Getting the correct medication and combination of treatment is critical to stabilizing so you can take advantage of other resources.
I strongly suggest at minimum a medication to treat the ADHD and probably an anti depressant (if directed) as depression is a very common comorbidity.
Once you have a stable level of medical support the next step is the mental support. For that I strongly suggest a cognitive behavioural therapy provider. The reason being building stable behaviours is key to reducing the impact of some of the issues that come with ADHD.
After that I got nothing, because I have personally not made it past this point, and have actually back slid some due to life. I am transitioning to a new Therapist so fingers crossed I can start to recover some.