So, hi. First of all, I would like to say that this is a glamorous and magnificent piece of artwork.
So, the colors are very vivid. Which is good. Too much blur wrecks things. I absolutely love the way you've made the Mad Hatter stand. Like, his feet placement and all. The detail on the Caterpillar's dress is very nice too. Simple, yet elegant. You've also made them look 3D. So they're actually people rather than a flat drawing. I'm not sure if I'm right, but the smoke from the cigarette covers his gun in a really epic effect. Which me gusta. :3 You say you can't draw guns. Yet that's actually a very good conception of a simple revolver. The shading on Caterpillar's face is hard to find, and you can only see it if you have sharp eyes or you're trying to find every possible good or bad point of this drawing (so... me). And the tiny amount of shading on her thighs, under her dress, is very nice too. I fucking love the Mad Hatter because he looks like Michael Jackson. His hat is SOOO AMAZING. Ohmagerd.
I don't know if it's meant to be like that, or not, but the smoke of the cigarette is in the shape of the gun. Which isn't normal. Maybe I'm being really picky, but Caterpillar's high heels look really 2D. I think it's mainly the one at the back. Beside the Mad Hatter's shoes. The face of the Mad Hatter is at such an angle, that when you drew it, it seemed to come out really weird. Maybe it's just me. But it seems freakishly out of place. Caterpillar's right hand (the one on the Mad Hatter) seems really weird. It's meant to show she's holding him, but it doesn't seem believable.
Maybe find pictures to refer to to draw smoke. The effect you made is nice, but let the smoke go a bit to the sides and higher. To make a really nice effect, make the smoke only cover some of the gun. So you see the shiny metal, then it's all blurred under the smoke. Try and use the same technique you used on the Mad Hatter's shoes to make Caterpillar's shoes look 3D too. I think it might be like that because of the light green color that the white highlights that give it the shine aren't as easily visible. For the face, try and Google images of people standing in that position. Or use Saucie as a model and take a picture of her to refer to. It'll help a lot with your work. Under Caterpillar's hand, maybe make it look like she's squeezing his clothes. So make wrinkles and make it look like the material around her hand is being pulled towards her hand. Like she's gripping it. If you know what I mean.
OVERALL: I'd say, 8.5/10. It's very well done. And from seeing your drawings every since you carried that notebook that was falling apart back in year 8, I can say that your drawings have improved A LOT. The number of POSITIVE points outnumbers the NEGATIVE. Which is great. And overall, it's a job well done. I hope you have more fan art from this manga coming soon. Because it seems you've found the most perfect selection of characters to make fan art of.