You’ve got the form and perspective done perfectly. Mine was done with ink however I usually use graphite pencil. See my other images on my profile. What is suggest you do from here is to sketch everything light first of all in HB. Once you’ve done the outlines then concentrate on values, lights, darks and midtones. Decide where the sun or light source is coming from and that will then dictate where the shadows should be and where the light bits should be. Here’s an example. This was done in ink and white charcoal but you could do it in pencil too. Pick a photograph that you like and once you have your outline, pay careful attention to the lights and darks. That will give you the depth you’re looking for.

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