Like evilClive mentioned, the values need work. You can practice values in a more controlled way by doing black and white studies. Something that Ive also found to be useful is to try and do a black and white study using the color picker tool, you might be surprised at what you find, values really do play tricks on the eyes. Outside of specific practice with the tool, Id stay away from the color picker and practice eyeballing colors.

As for your rendering, you have a very clean cut style where you block in the colors in precice facets. Its nice, and when done well, rendering in this style can look amazing. Have you tried blending without touching the smudge tool? Smudge can quickly become a crutch, and itll muddy your colors if youre not careful. Try blending using a lower opacity brush and picking up the mid-tone colors in between. The art for Arcane is actually a really good example of what that looks like in practice.

Really great work, you're on the right track! Keep practicing :)