For me personally, I don't need a lot of tbsps to get the desired effect. I usually knead 1/8 of a cup (2 tbsps) in 1 and a half cups of water, and two batches of that is usually good for the night. That's regular kava powder though, not micro or instant. Those might be different.
You might find that the longer you drink kava, the less you need. I did. Reverse tolerance seems to be a thing.