You can also make a prop balancer to use until you buy one. All you need is a thin, stiff piece of wire. (One that will fit through the hole in the prop hub.)

Hold one end, with the prop on it, and give the prop a slow spin. Note which blade stops in the down position. Do this three or four times. If the same blade stops in the down position, that is the heavy blade. Sand the back of the blade and try it again.

A properly balanced prop will have the blades stopping in about any position, but never repeatedly with the same blade down.

By the way. Diameter = torque, grunt, pulling power. Pitch = speed. (As has been said.) A general rule of thumb; for every inch you increase either diameter or pitch, you should reduce the other by an inch. That's why we said 10 X 6, or 11 x 5. Theoretically, a 9 X 7, or a 12 X 4 will also work. (9 X 7 = greatest speed, 12 X 4 = greatest vertical pull.) But there are limits where engine efficiency prevents theory from working.

A lot to absorb, but you'll get there.
Dennis-