iVolks Fast Wireless Charger
If you're looking for a decent and well-rounded charger, this one from ivolks is a good option. It won an Amazon Choice Award and has tons of 5-star reviews.
This little wireless charging pad does 10w fast charging with Samsung devices or 5w for other phones. It's only 8mm thin, so it's a little thinner than your Galaxy S9. The company added a notification LED, rubber feet so it won't slide on a table, and kept the price low. Basically, it's a good little cheap but effective fast wireless charger for Galaxy S9 or iPhone owners.