Not bad at all for a first shot
The first thing I recommand, is to go to Deviant Art and download brushes (Or you can go to check Humus' sticky), Try to give a 'meaning' to your background, make it represent ''something'' , if you know what I mean. Plain background are fine for starting, but if you want to aquire more experience, I'd try to stick with more complex things
For the text, It's fine, yet a bit too simple thought. I'd try to add strokes, it always add a nice ''finished job''. Plus, to make it more blended, I'd put the oppacity to around 80-85%
Blending job of the render is good, The red suits perfectly. I personally love to add lightning to my signature, it's always catchy for the eyes
As for the size, it's kind of large, but I also prefer to work with bigger signature, to make more details. But the story is different since yours is a bit plain.
A final note on the background would be the colors. Anubis always used to tell me that Red and Green dont go well together (unless it's Christmas Releated), Althrough I would have to disagree abit, because I think it's actually look pretty good. But the only thing is; The red is too bright compared to the green.
Not bad, alot better than my first (trust me, it was horrible

)
The more you will make, the more you will gain experience and get even better results
Have a nice day.