The background doesn't really blend well with the character IMO, I feel like the colors and brightness are off. I'd work on blending first because its one of the most important skills you need to have when working with images. There are lots of ways to do it and each method won't work for every situation, you need to learn alot of different styles, and tutorials on deviant art and other websites will help alot in teaching you how to do this.
I'm also not really sure what the focus of the picture is, I don't see it as a whole picture without trying and there isn't a lot of consistency between the images. I feel like there's alot of space here that isn't necessary and it makes it hard to view the two main elements together. One pitfall you might encounter is picking a background and trying to build an image around it. Instead you should pick a focus point and build your image around that focus so that the whole thing complements itself.
Next, the text. Text is something that can make or break an image and is also a very hard skill to master. Try and find some fonts that match your project goals on sites like dafont and others, there's an unlimited amount of fonts out there. Blending your text in to the background and overall making it complement an image instead of contrast it is gamechanging. Also don't be afraid to use some of the blending effects on your font. A well done bevel&e or drop shadow can really make a good font fit your image and is an easy shortcut for when your first starting out.
In this picture your text is very bland and I don't feel the font and effect matches the picture at all.
Lastly, work on editing images better, try zooming in to increase your accuracy, and clean up with a low pixel eraser after like others have said. It isn't as noticeable here, but when your working on ou blending and effects the extra pixels will really stand out and can ruin a project.
Ultimately, it's a great start and I hope you stick with it as photoshop is a very valuable skill to have if you work or are a student for a living. I was able to self teach myself using the Internet and now occasionally work as a freelance designer for a few websites out there while complementing my schoolwork and educAtion. Sorry for any spelling mistakes, I typed this on my phone. Goodluck.