You really did a great job on your first sig!
I like it, especially that you have a light source there. I remember my first sig it was meh xD
Also if you really want to make your sigs better, try looking for some tutorials you can find tons of them in deviantart. You can start simple like getting used to brushes, adding depth, blending modes and gradient maps and if you get into it you can start learning some technique like smudging, adding textures/ c4d renders, vectors and such...
Just keep practicing
...well opening a shop might help you with your practice. A well made siggy will always be awesome xD