First of all: the hands and the rings look awesome. Especially the rings have a lot of detail and are nicely shaded.
It would have probably been a better idea to start with a better reference picture. His head is tilte to the back, which is rather hard to draw, especially for a first time. Because of this, the head looks out of proportion: the nose looks too small and the mouth looks too big. The irides are out of proportion too - the left one is larger than the right one and don't look round to me.
Try to draw the hair too next time, it looks unfinished like this. I really like the shading between the left eye and the eyebrows, try using that in the rest of the drawing, it will probably give it more dimension.
Edit: I just noticed this wasn't a CnC and I did give quite a bit of criticism. I'm just trying to help you. It already looks good, especially for a first portrait, but maybe you can use this for your future drawings.