There has been a release of OTG Flash drives recently(not too recent though) for those who would like to expand their storage, I got myself an iPhone 6 that had only 16gb, it saved me alot of money getting a 128gb OTG flash drive for my phone, at least I could now save important files and open them with ease, instead of getting a 128gb for some huge $$$. The main advantage of an OTG drive is that, OTG allows device such as a smartphone to use the same port to charge it up or to synchronise with a computer (where it acts as a device to the computer host) and also to plug in USB devices such as memory sticks ( where it acts as the host controlling the device).

You are really gonna love this if you want an easy way to move files to and from your phone without having to delete them because of low storage.

http://www.ttechbay.com/2018/06/09/dont-delete-your-important-files-because-of-low-storage-space-try-usb-otg/