If you mainly use dropbox as a way to share files between devices, than you could consider setting up your own "cloud" (NextCloud is open source and quite easy to setup yourself (in combination with XAMPP or similar tool.)). Besides an online interface, it comes with clients for iP(ad/hone), Android, PC, Mac and Linux.
But if you mainly use dropbox as a way to store data off-site, then hosting your own "cloud" isn't such a stellar idea. Setting up your own "cloud" is initially a headache and you remain responsible for maintenance/upkeep, it also gives you much more control to share data between family and friends, if you so desire.
First, make sure that if you setup your "cloud", that your ISP doesn't object against such things. Or that you don't exceed the limits of your metered internet plan, if you were tricked into getting such a type of internet connection.