A set of three Aukey Type-A to Type-C USB cables is just $7 today
If you didn't have a USB-C powered device last year, chances are you will before the end of 2018. That means you'll need Type-A (i.e. standard USB) to Type-C cables to make all of your devices and chargers play nice with each other. Today, Aukey via Amazon is selling a three pack of 3-foot USB 3.0 Type-A to USB Type-C for $7.
The sticker price is $10, but if you click the rebate section underneath the price, then click Redeem, you'll see an option for "30% off 1 item(s)".
These cords have not been examined by Type-A to Type-C guru Benson Leung, but they are from a known company with many happy customer reviews and the right specs. In other words, these wires should be safe for all your USB-C electronics.