You started with what is possibly among the most difficult genre for a beginner, portraits.
Anyway, with a frontal self-portrait like this it may be slightly simpler to start with.
First of all just consider that a head is an ovoid, as a general shape, therefore, if You can give the right tones in the right ranges of a ball (higlight, various midtones, shadow line etc. (ball drawing excercise) just consider where the light comes from and think of a face like a distorted ball into ovoid for tonal scheme.
Obviously there are quite a few parts on a face and the most tonally meaningful are shadows possibly casted on eyes by the front, the nose, a sort of pyramidal form plugged on the ovoid and the ovals containing eyes and mouth or the round surfaces of cheeks superimposed on the ovoid as well.
Since You don't ask for a manual but how to increase 3D impression, these indications should suggest where elaborate on tones and how to increase the tone range in case.
remember also that our face isn't too much symmetrical (to improve likeness) and that hair should be started as larger volumes with their relevant tonal scheme and only later suggesting hair by drawing enough of them (not them all or too many) according to how they may show the impinging light or shadows.
Your outcome is a very good base for "daring" more and work according to the above ...
Panta rei (everything flows)!