Hi Citrus,
I'm glad you have decided to delvelop your skill, and this forum is a great place place to start, so welcome.

Using your imagination is fine, but I think you need to use referances initialy, just to get a feel for proportions and some of the important details.
Your drawing has a few things which are just not correct, for instance, his right hand appears to be on backwards, and his left hand appears to have 6 fingers.
I would suggest starting with a simple subject, do the line drawing using a grid, and get this as accurate as posssible.
Then take your time to shade and blend exactly what you see in the ref photo.
Post the various stages, and get help as you need it.
I hope you continue to draw and post here, you can improve with help, but you need to practice practice practice.
Looking forward to seeing more from you.
