I also have ADHD and Obsidian has been very helpful. I also lost a lot of time tinkering with it at first, but that kind of helped me in the long term because I am now so intimately aware of what works and what doesn’t. Plus it was so fun tinkering, I now have good associations which makes me more likely to open it and get started on my work (tricking my adhd brain with whatever I can, LOL.). From an ADHD perspective, picking a theme that you like really helps on that side as well.
So - if you’re having fun with the tinkering, don’t kick yourself for getting lost in the weeds, let your brain draw positive connections so you can return to obsidian for productive things. If it’s just stressing you out, decide what you most want to use it for, download associated plugins, and ignore everything else for now. I like Dataview, Outline (a core plugin), Automatic Table of Contents, and Checklist.
I recommend really leaning on Dataview (lets you essentially create a database) and adding metadata to all notes in a structured way. When I built the vault for my graduate degree, I created a few notes templates according to my needs (one for each of these types: general notes, maps of content, meetings, articles, writing projects). That way you can start new notes from templates, with metadata and a structure already included - you immediately skip that first step.
Every template has a summery section in the metadata so I can use dataview to create tables with summaries of my notes. I have a tag system that I try to keep consistent across the vault so I can also use it for dataview and searching. The point is to simplify everything so you can quickly find a relevant note.
Each section of my vault also has a map of contents with a bunch of dataview tables tailored for whatever project it. Most importantly, each map of content has a table with the 5 most recent notes I’ve edited, and summaries of what they are so I remember what I was doing. (I love the breadcrumb idea from groberts56, also a very cool way to stay on track!) If you can set it up so it’s clear what you have to do next, it makes a big difference.
Good luck! I hope the ADHD diagnosis is helpful (it was for me) 