My personal favorite apps for editing photos for social media, creating recognition posts ( CANVA.COM is a great website and has an APP although the app is more limited than the site)
I suggest investing the extra $1-5 for some of these apps to remove the watermark.
facetune, snapseed, afterlight, VSCO, party party, instasize
Pic-post-play, iMovie and lomotif is great for adding a 30 second video to a clip. Don't share to Facebook because of copy right issues!
Recognition/ TEXT overlay:
wordswag, over, Rhonna designs
More on how to use your phone for your online office but how I use apps for editing!