I was in similar situation, where I would sleep off daytime, then it messed up my sleep schedule for years. I got better once I realized that I am a zombie in that state. I advise going for a walk. Try to go a bit further every day. Just stop outside, it's funny to go home instantly, so have to walk for a minute. The this has two benefits - cardio on fresh air is good for physical health and makes you tired for the night, and for me it brought relief from mental pressure and gave space that I am safe to think about difficult stuff. There is something in act of moving that help with the head. It's also nice anchor - you are in control of his much you walk, where you walk, just do it, like guy from memes.
Be kind to yourself <3
Everything that you use for prolonged amounts of time every day. For me it was ergonomic chair, keyboard, pillow. Expensive is a word, but I would rather think higher quality when choosing replacement for stuff I use.
Another category of things is hobby equipment, for me it's instruments. When I buy one it's to last. So when I was buying digital piano I went for one over my budget because I don't plan to get rid of it for next 5-10 years still, and it was 5years ago. Overall stuff that you don't usually think of buying frequently.
Last category I think of i go for higher quality stuff then generic ones are travel stuff. Last thing you want during your trip, short or long, distant or near, is to deal with faulty bag, broken wheel, or such.