GIMP is free and it can do a lot, I used it for everything for many years, but it is not that easy to use, you will need to do a lot of research on how to use GIMP to do X. I think Lightroom is the most efficient, all purpose program, but it doesn't have layers and there are things it cannot do. Photoshop is the most powerful, and I use it a lot, but it takes more time to learn and to use. I'd say start with GIMP and learn how to do some things, then get Lightroom, then get Photoshop.