Hey nice artwork you got here.
Reminds me of my own artwork a few years back. So I think I can help you with a few things here.
1. Looks like you drew it on paper, digitized, and then colored it on Photoshop (or similar software). I did it just like you a few years back, so I can tell. The problem with your colouring method right now, is that the lineart is dithered and uneven, as it follows exactly (or almost) the paper version. Some places is thicker, others is slimmer. While having thicker and slimmer lines in certain places is okay and even encouraged, in your case it is just random and looks bad. So let me recommend you a colouring tutorial.
After following this tutorial, you will improve your lineart not only on digital version, but on paper version as well (because it will start being a concern to you). Try viewing some awesome manga drawings once in a while and also YouTube videos of people drawing them, it will give you great inspiration and you might start to understand how lineart works (where to make lines thicker, slimmer, etc).
2. Try copy. Not necessarily the whole drawing, but try copy the parts (eyes, pose, muscles, etc) from DBZ pictures on the internet (seems like your style? ), exactly like the original. This will make you notice details you did not notice before.
Overall, you are in the right path and surely have potential! Usually I start by giving advice on the steps for drawing (sketch, lineart, details, shading...) but seems like you are over this phase already and only need to improve the details and perfect yourself.
Reminds me of my own artwork a few years back. So I think I can help you with a few things here.
1. Looks like you drew it on paper, digitized, and then colored it on Photoshop (or similar software). I did it just like you a few years back, so I can tell. The problem with your colouring method right now, is that the lineart is dithered and uneven, as it follows exactly (or almost) the paper version. Some places is thicker, others is slimmer. While having thicker and slimmer lines in certain places is okay and even encouraged, in your case it is just random and looks bad. So let me recommend you a colouring tutorial.
After following this tutorial, you will improve your lineart not only on digital version, but on paper version as well (because it will start being a concern to you). Try viewing some awesome manga drawings once in a while and also YouTube videos of people drawing them, it will give you great inspiration and you might start to understand how lineart works (where to make lines thicker, slimmer, etc).
2. Try copy. Not necessarily the whole drawing, but try copy the parts (eyes, pose, muscles, etc) from DBZ pictures on the internet (seems like your style? ), exactly like the original. This will make you notice details you did not notice before.
Overall, you are in the right path and surely have potential! Usually I start by giving advice on the steps for drawing (sketch, lineart, details, shading...) but seems like you are over this phase already and only need to improve the details and perfect yourself.