Most phones come with at least 32GB nowadays, with 64GB being the standard for flagships and 128GB available as an upgrade. But if you need more storage - and by more, I mean a crapload more - SanDisk's 400GB Ultra microSD card has been discounted to $189.99 today. That's $60 off MSRP, though you'll have to be willing to wait a few weeks for it to hit your doorstep. 256GB and 200GB cards have noticeable discounts as well.
SanDisk released the massive 400GB card right at the end of August last year at IFA, setting the MSRP at $249.99. Needless to say, it's a top-notch card; it's A1-rated with up to 100MB/s transfer speeds. This 400GB card usually hovers around the high-$220, low-$230 mark, but it's now dropped by quite a bit to $189.99. The 256GB version usually goes in the low-$120 range, but it's currently $99.99. And the 200GB card is usually up near the $70 mark, but it's now $62.99.
If you want a 400GB card, just be aware that units are slated to ship in two to four weeks. 256GB and 200GB versions should be shipping right away. Shipping is free. Throw any of these into your phone (unless you have a Pixel, in which case nope) and you'll probably never have to delete anything from your phone ever again.