"Mehr Licht!", as Goethe would say. Lighting is very important and it's one of the best bang for the buck things you can do.
Good pens. I always buy pens and experiment with different types. Every pen has a certain flow and friction required to deliver ink. For people who don't write a lot, this is unimportant. If you write a lot, it becomes palpable. Does the pen just roll and write, or does it need to be "pressed" and "pushed" to deliver ink. Does it dry quickly? Does it "shit itself" and smudge: when you trace a line, by the time you get to the end of the line, did the pen deliver more ink than necessary to trace a line and form a sort of drop around the tip? It will be messy. You have to clean it on a sheet of paper or that ink will find its way on the next thing you'll write. Does the ink stick well and survive a drop of water or a tear for example : )
Good notebooks: are the squares small and noisy? Do you use the same pen color as the notebook lines which makes it harder to read?
A good headset. I record our video calls and I used to have a Bluetooth headset, which meant I couldn't use the microphone (I'm on Linux). We bought another type of "wireless" headsets where you plug a dongle (SteelSeries Arctis 1). They're cheap, but now I'm recording from my headset's microphone, not from my laptop's. Which means the noise of the fans doesn't make it to the recording. The fans are really noisy (when you do Jitsi + OBS for recording).