I only really like Anker USB because it's compatible with hardmods... Otherwise, get anything with a fast write speed, so you can transfer large roms/nand backups quickly.
As far as the SD goes, I think this is the cheapest/best solution:
http://www.amazon.com/PNY-128GB-Mic...e=UTF8&qid=1461475092&sr=8-1&keywords=pny+128
8gb or higher is highly recommended, 64gb might cause you to install too many games and never play them, 128gb can give you slower boot times with a9lh installed, and class-10 write speed is pretty good. Keep in mind that N3DS can
only use microSD, while O3ds can use both a large sd and a microsd-to-large-sd adaptor