If you have a compost pile you probably dump your coffee grounds there. And pile or not. You can get get the benefits of the grounds by using them as a top dressing. A few tsps. sprinkled on top of your medium and watered in every 2 or 3 weeks and your plants will love you. I like to allow mine to dry out before using. Easier to spread evenly. Just remember it is a nutrient, so treat it as such...
PS-If you have a fungus gnat issue I would refrain from using the grounds until the pest problem is under control. No need to feed the enemy...