If functionality and cost are your two biggest buying factors, you'll want to consider Samsung's old style of wireless charging pad.
These charging pads look like mini-UFOs and are Fast Charge-compatible for devices that support it such as the Galaxy S9. It also comes with a Samsung 2A wall charger — always great — and comes with a standard one-year warranty.
This is a great option if you're looking to set up wireless charging at your home and at work because they're so damn cheap right now. You can also get the older style as a charging stand ($50)if you prefer that look instead. You may also want to consider this bundle which includes Samsung's car charger along with two cables (Micro-USB and USB-C) for just $39.99 ($40).
Source : https://www.androidcentral.com/best-wireless-charging-pads-samsung-galaxy-s9