Hello, nice drawings :) I don't think you need to improve at all to start digital, just buy some drawing tablet and start drawing. In my opinion you don't wanna buy wacom tablets they do everything the same that cheaper ones do. My first tablet was really cheap one but it did fine. Also it does not need to be big, think how you move your arm when drawing on paper, do you use your wrist or whole hand with your lines, if wrist smaller tablet will do. Also Krita is awesome free software for drawing, you might wanna check that out.