Recently one of my former students, Jonathan, inquired about photo processing software. He was particularly interested in Adobe Lightroom, but was concerned about the best way to get started. He thought it looked too complicated, which at some level I would agree, however once you understand the basics most of the image enhancements and corrections you need to do routinely become second nature. When I began using a digital camera over 15 years ago, I used both Photoshop Elements and Paint Shop Pro. I eventually, after learning the basics, locked in on Photoshop Elements, then after several years Adobe Lightroom and Photoshop. I have a colleague who has used Paint Shop and his work is simply brilliant! My advice is to start with Photoshop Elements, it relatively easy to learn. The following link is a little out dated it does outline several other choices. Beginner photo editors for windows. While the link is for Windows, several of the programs listed also work on a MAC. I also understand, as photographer friends have told me, that Snapseed works well on both the iPad, Kindle and Android Tablets, but frankly I have no experience editing on these platforms, as I prefer to use the computer for all photo processing.
Adobe Lightroom provides an excellent way of cataloging and non-destructively processing your photos. This link provides a short summary of the best-non-destructive editing-software-for-photography from Photographylife.com