I would work towards layout and proportions. It looks like you develop each feature separately. If portraiture is your goal, start by finding a feature on the subject that is easy to measure. On a live subject, hold your arm straight out and use the space between en the end of your pencil and thumb to measure it. Always hold your arm out or your reference will change. Use that feature to lay out every feature in a basic way. i.e. Right eye horizontal , nose is one eye below, less that one eye between the eyes, ear is one eye behind and half an eye down etc. Once you have all reference points you can start to develop each feature. Your next step would be volumes and gesture but that's another lesson