You youngbloods have come a long way from where most were when I was one. I saw this in the case and thought "man, to have been able to paint that well 10 years ago."
My personal thoughts, so take them for what they are;
A Death Jester is typically a darker, more sadistic harlequin. I don't really see the yellow being a good fit for him in that respect, other than the fact that teal and orange just look good together in general. Furthermore, I don't think the orange as a shade is working; I would have taken it darker in the folds, and pulled the orange out for the higher points, rather than carrying the blend all the way up to near-white.
Your NMM on the base looks great. However, on the gun, you didn't take your shades deep enough, and your proportion of highlights is much higher, which took away the believablitlity of the metal.
Next time you're out somewhere, take a look at the chrome on a car and watch how the reflection shifts as light hits it. The more you do that, you can start to get a visualization of how that plays out in life in your head, and you can start to imagine the piece you want to paint being made of a reflective metal in your minds eye. Then you just have to paint what you see.
I don't think any of the things that detract from the figure are due to anything fundamentally wrong, though. I think over time, as you paint more and more, your instincts on color palette will see you through very well. You produced a really good piece, far better than a lot of things I see adults paint, and I look forward to seeing more from you in the future.
Keep up the practice, and I foresee you being someone that racks up a lot of daemons over the years.