I LOVE my beauty blender. It flawlessly applies my foundation and is great for blending.
You may think $20 for a sponge is a little pricey but, in my opinion, it's totally worth it. I have had mine for about a year and a half and it is still in great shape. It's reusable so you never have to throw it away like other sponges.
Get it wet before using and squeeze out any excess water. Using light dabbing motions apply your foundation all over your face. The beauty blender is also great for building, it doesn't apply too heavily so you can always go back over an area if you need to.
The packaging is also great because you can set your beauty blender on top of the case when it is wet, until it dries. This way it does not sit somewhere else attracting dust and dirt. Then once it is dry you put it back in its little container and pop the lid back on!