Focus on the overall big shapes of the figure first and figure out the 3D forms for them. For value and lighting, I usually go from top to bottom, light value range on top, darker value range on the bottom, and then add rim light to highlight the figure. since this character is full of different texture and materials, I strongly suggest you to have lots of references and do a lot of material studies. The metal you have is quite flat and considering the amount of metal on the character has, I think you should focus on more on how to render metal. Also more story telling side, you can add chipped and scratches on the metal, like on the axe. Overall the design requires quite an advanced understanding of materials and texture, so really try to focus on that when you work on this.

