I don't think Gimp is the best one for photo editing. I like photography and often take photos with my camera. I would like to edit photos on my iPhone. The apps VSCO, Adobe Lightroom, Picsart, Snapseed are my favorite. VSCO is stark for its filter feature. Picsart is a fashionable one. Snapseed is a really photo editing app that allows you to edit photo effect, to crop photo ratio, and more. These apps are also user-friendly for beginners. You can have a try.