I think I should have commented on this LONG ago. *fails* But... I will give... A CRITIQUE. O.O;
Anyways, I must say that hours and hours of sketching are obviously noticed. Nor mentioning your adquired and now obvious shoujo style, I love the details you tried to give the picture, even if it's all "messy" and "sketchie".
The brush you used for Videl's hair was the right one. Makes her hair fall awesome over her shoulders and arms, although just as you gave her upper hair some hints of light falling over, you could have done the same with the pigtails. That would have given a better effect of movement. Apart from that, I don't have any aditional comment on Videl.
Now, Gohan-kun... How I love him. I like the effect of the two "expressions", so we're able to notice how wide are Gohan's eyes behind his saiyaman mask. The effect of reflect you put on him was good and you must continue practicing. It will help you to know where to apply shades, or in case you want to continue this style, to add some textures or B/W backgrounds.
Maybe it's me, but from the perspective of his face and stuff I think the chest is a bit too broad but... not that I mind about it. LOL.
You have still to practice the use of white brushes when two black objects are close or overlapped. It's clearly seen that you filled it after drawing and it has some parts without coloring that might substract some points of your hard, great work.
I think I have nothing else to say, and I hope you enjoy my attempt of critique. Bye!