VRS Design Slim Armor ($11)
If you're looking for something sleek, thin, affordable and unassuming, consider the VRS Design Slim Armor.
This case is a single layer of durable TPU material with multiple different finishes for a unique look. VRS design added a smooth finish to the case, glossy edges for a premium look, then a soft brushed finish texture to the back part of the case. That way you're protected, the case looks fancy, and it's thin at the same time.
TPU cases are some of my favorites. This case has oversized buttons for ease of use, and a small lip that wraps around the front of the screen to keep it safe. You can lay the Galaxy S9 flat on a table and the screen will never touch. Then, the angled cutout for the fingerprint scanner and camera will ensure you touch the right area. It's a great overall case at a wallet-friendly price.