I like Google Docs and Google Photos. You can set you phone to update automatically, and then clear out your phone's memory. Stay aware of how it all works and actively manage it or you could delete something you haven't backed-up yet or upload something you don't want to to somewhere you don't want to when you're just trying to share a picture or resume to edit with a friend.

Also note that despite what some of us think about Google, they don't actually give us unlimited storage. I actually hit my free limit accidentally a little while ago, and because all my Google stuff is linked together, all of it stopped working until I deleted content, including gmail. (Luckily, my problem was in my laptop upload settings so was easily fixed.)