It depends on what you want to accomplish, if you're interested in design, creating artwork or you're more focused on productivity and batch editing.
You didn't say why you gave up on Photoshop. If you didn't like its interface, I don't think you'll be thrilled with GIMP. There's no point in repeating what others already mentioned, so I'm going to recommend other tools worth checking out.
Fotor has a desktop version for Windows and has a pretty good set of features. Good basic edits, a good range of effects and an option to create collages.
BatchPhoto is an alternative to Photoshop from a batch processing perspective. It can resize, watermark, convert or rename dozens of images at once. It also has features to reduce noise, sharpen your photos or adjust the light intensity.
Hope it helps.