Next up is a proper table and a chair with proper back support.
I would suggest you get a bigger one. I mostly spent my whole day here so a bigger one with enough empty spaces lets me utilize it for my other needs, like studying, lol.
I am looking forward to seeing which chair you pick.
Something slightly bigger will do just fine, the current one is quite big already.
A good office chair, mesh back, metal frame and all, within 10k to 15kish range.