Wow that's prety impressive for the first time ever using it. I like the conecept of it. There are some little mistakes in the border of the hands layer, as was pointed out, but it was pretty good overall. One thing I would do is smooth out the sharp edge between the glass orb thing and the background (if you zoom in, its very sharp.The simplist way to do this would be to get the eraser and make it say 50% fill and erase the edge a little bit. Or, you can select the edge of the layer, select the inverse, (control shift I) and then right click refine edge (control alt r i believe) and you can feather the edge outwards, so it selects into the layer. Then delete this selection (just hit delete) and it will erase the transparent part outside of the layer, and soften the edge a little. You can undo if it looks too extreme and tweak the settings again in the refine edge (think that's what its called) window that pops up. This will also fix the little errors where you can see the white background.
Definitely watch some tutorials on youtube, they can be really helpful.
"take deoxyribonucleic acid for example. Sound's impressive right? Ever see what happens when you put something in acid? It dissolves. If our bodies were all full of that acid, we'd all dissolve. So much for the theory of evolution."