If you’re considering purchasing filters, I highly recommend doing some initial research on how specific brands and systems work with the lens or lenses you’ll use it with.
Focus Stacking is Your Friend
A common approach to wide-angle landscape photography is to have a low perspective, a foreground element close to the lens and a background which is equally important. Maintaining a sharp focus on both an object close and far away from the lens can be challenging, even when using a hyperfocal distance.
Focus Stacking for a greater depth of field is a popular workaround for this problem. By capturing multiple images that focus on different places throughout the frame and blending them together in post-processing, you’ll get an image which is razor-sharp from front to back.