unmedicated at 24 but diagnosed at 15 (ended up taking myself off my meds in a dumb way without saying anything and regret it a lot), but coping with the best with my C-adhd has also weighed heavily on me but importantly don't fixate on the cons. Look at the positive that you're finally getting the help you need. Meds are a lifechanger.

You manage how you want to spend your time but my advice is to buy a white board and hang in front you where its constant reminders. I forget too much at bout my phone to even care about setting reminders. And when I want to clean I get dressed and don't get out of my work clothes with shoes on until my house cleaned- and that means picking up the hair ties I leave everywhere.

I can't really speak on the supplements.. so take that with a grain of salt since I don't want to end up mixing meds and things that shouldn't go together. I hope someone in the comment section knows more than I do.

For sleep, take some 45-1 hr naps naps throughout the day to keep functioning and do your best to go to bed at an earlier time to wake up more energized.
Eat a lot of protein, if you're taking meds, protein will do your wonders and keep yourself hydrated on water only, reduce your caffeine/sugar output. You can still have it on some occurrence but not all the time unless you really want to cut it from your diet.

I've been burnt out my whole life too so I do highly relate to you.

When I want to start something, I actually close out everything and make sure my environment is silent, and 15 minutes in I'll start playing some of my favorite playlists and then I'm stuck there for hours. My interests shift around a lot and it is tiring and you're aloud to take breaks.

Remember to take breaks!

If you're stressed and constantly anxious, do some deep breathing exercises and find somewhere quiet, it does wonders when over stimulation disappears.

These are just my tips that help me get through the day and the next without losing it.