If you want the most performance at a reasonable price, it's the Samsung EVO+ (EVO Plus) series, hands down. They aren't the cheapest, but they aren't over the top expensive either, and they will outperform cards several times their price. The thing that sets them apart is their random I/O performance. Most SD cards and USB flash drives are highly optimized for sequential I/O, but a lot of data I/O done by computers is non-sequential, and most SD cards and USB flash drive have truly horrible non-sequential (random) I/O performance.
Now if all you want is the most storage for the buck, there are cheaper alternatives.
For performance, the Samsung EVO Plus offers the best bang for the buck by far, and on my Pi3 the difference is very noticeable. I usually get the 32GB, and in the USA they run around $15, but can be found on sale for <$10. Beware of buying them off of ebay, as there are a lot of counterfeit Samsung cards sold there (especially in the larger sizes).
My mind is like a browser. 27 tabs are open, 9 aren't responding,
lots of pop-ups...and where is that annoying music coming from?