Best simple photo manager

Im converting this website to wordpress for a client of mine:
https://www.snapclicker.com

At the moment, i have each portfolio gallery as separate pages, what would be the best simplest photo uploader plugin to manage photos, it has to have a simple frontend, since i already have the CSS&HTML and lightbox how i like it, it just needs to have a powerful admin backend, and a simple image output for the pages…

Thanks.

– Tom