The "less is more" approach really works with stevia. The type of powder i use came with a little tiny "spoon" in it. I use about 4 heaped tiny little spoons per half gallon. But I always start with 3 then taste. I've never measured in a real measuring spoon, but I can try...... looked like a scant 1/4 tsp. Maybe try a 1/8th tsp. then add more to taste.
I admit that stevia does have a bit of it's own flavor, but so do all the other sweeteners.
The "aqua frescas" type Kool-Aids have a very light taste... more refreshing than flavorful, that's why I like them... my DH says they are nasty. LOL

=)
Cori