krita tutorials actually give you a pretty good starting point on that so you won’t need much else at the start, they are quite good at that! And then there are tons of resources out there to look for specific things you would want from qt but haven’t found yet in krita or qt documentations.
Official krita scripting tutorial is a pretty solid point to start actually, you can find it here: https://scripting.krita.org/
and if you would want to develop plugins this is essential plugin to have: Python Plugin Developer Tools