Need a good photo app for iPhone that keeps pics after I download to computer?

Not looking for filters or editing features. What I want is a good photo app that lets me keep some pics on my phone (iPhone 5C) after I download everything to my computer. I want to keep certain pics on the phone to keep with me and show people, but after I download the ones I've taken (over 500), I can only choose to save all or delete all from the phone. And its a huge pain to keep them, then delete them all one by one on the phone. Is there an app that lets me "tag" the ones I want to keep on the phone, or put them in a separate area that doesn't get deleted, or have copies of the ones I want to keep sent to a different area?

Its pretty easy to delete all, you can just connect to computer and use windows explorer to highlight and delete or copy all… Simple.