GIMP

If you need a low-cost image editing tool that nearly rivals Photoshop, then you can't go past GIMP. I have used it for years as my photo editing tool of choice, and there are still some things I can only do in GIMP. I have recently started using Affinity Photo - mostly because it is more non-destructive than GIMP - but if you duplicate layers and save backup copies of your work in GIMP, it's really not a big limitation. I'm now learning my way about AP, but even still, I find myself opening GIMP regularly to use it for the things it does best. Definitely a tool worth having in your arsenal, and it's free. Once you learn how it works, you'll see how powerful it really is.