Having more storage is never a bad thing, but that doesn't mean you should buy it on a whim. It's smarter to wait for a big sale, like we have today on Amazon Goldbox. A variety of SanDisk cards and flash drives are on sale for up to 71% off.
One of the most attractive deals today is for SanDisk's 256GB microSD card. It's only $116.95, down from $200. That's 42% off. You can also get the 32GB card for a mere $11.15, down from $26.84 (71% off). There are various regular USB drives, which won't do you much good on Android unless you haul around a converter. However, the SanDisk dual drives are included. Those have either a microUSB or Type-C connector along with a standard Type-A port. These are between $12 (16GB) and $21 (64GB) for Type-C and $29.59 for a 128GB microUSB version.
Amazon is also discounting some of SanDisk's Connect wireless drives. These devices produce a WiFi hotspot with built-in storage. They're a bit spendy even with the discount ($55 for 128GB and $144 for 256GB), but you can share files with multiple people.
As with all Goldbox deals, these are only valid today. All of them have Prime shipping, too.