Hello and welcome! Doing a Dungeons & Dragons type like project, yeah? Good times, I love seeing things in that sort of fantasy genre. That's a Tiefling yeah? I hadn't meddled in D&D in years, and years of years within years, I'd forgotten the race name, but then there's Google.
I have some input on the sketch, and to begin, the body proportions are not bad, but the arms are disproportionate and awkward looking, and the walk does not look natural. On a side note, I do like the costume design. The face I see you definitely struggle with the most, because it's the most disproportional. So much so, the only thing that's going to help you is to use your daily sketch time to draw portraits for a while. Particularly practice expressions. It's not as fun as drawing from your head, but definitely more useful as a learning experience. What I use to do to make it more interesting for myself, is I would pause on random places in music videos, because musicians almost always have strange and fun expressions when singing.
Your color choices look very nice to me, there's nothing too harsh or overbearing about the pallet. Highlights will definitely do good in bringing forth the detail. Don't be afraid to use more intense shadows to bring out the form. There are many digital painting tutorials out on the net and you'll find quite a bit if you use even Google by simply typing coloring tutorialin the image search engine. I myself usually like to start with a dark base and bring out the form with highlights.
Keep it up!