I had good success with the freely downloadable Paint.net which, along with Photoshop & others, allows 'layered' graphics. Layered graphics are very easy to use and can greatly increase the quality of your designs.
For my designs I developed some useful techniques which I posted and summarized in the link below. Check out the link-list in the 2nd post in the following thread (though I encourage to read the entire thread to see how well someone in a similar position to you fared)...
http://www.ootpdevelopments.com/boar...-uniforms.html
To see if you'd be interested in these techniques, I'll include a small sample of what kind of uniforms you can design.