Microsoft OneDrive offers a generous amount of free storage for my files that can be accessed from almost any device - iOS, Android, Windows or web.
If you're going to use it for work, or if you need a lot of storage, you might want to pay for an Office 365 subscription, it gives you access to the latest full-featured Office apps - Word, Excel, PowerPoint, Outlook and more, 1GB storage space on OneDrive and the Teams app for collaboration (Slack competitor).