Great start mate... watch the shoulder areas the lenght of the arms, they are a bit short from the look of them......
The realistic look will come just make sure you get the proportions rought out first, the rest is just adding ading and pulling verts.
I am enough of an artist to draw freely upon my imagination, knowledge is limited, imagination encircles the world. (Albert Einstein)
https://www.artstation.com/kurtb