I recommend Photoshop Elements. You can download a trial version to see if it is right for you. There are many free tutorials available online as well as free add-in/enhancements you can install to add more features. Also quite a few very good books available....many of us DISigners use it!!
If you love it, get very good at it and have the $$$....you can someday move up to Photoshop but it does cost hundreds of dollars.