Hi there! Your first mini doesn´t look half bad! It could improve a ton just using inks (they don´t require any skill and create instant shadows)
For flesh, try using Reikland fleshshade
For metallics and browns, Agrax earthshade
For reds, Carrobourg Crimsom
For Blues, Asurmen Blue
That is what works for me. Another useful and easy technique is dry brush, it would be the next step after inks.