The "right" sign for "ball" depends on what kind of ball you are talking about.
If you are talking about "a ball" as in "a dance" then you might sign "DANCE" or just spell B-A-L-L.
If you are talking about a large ball then you will need to do the sign larger.
The generic sign for BALL can (in context" be interpreted as meaning "softball."
BALL (generic)
Note: The concept of BALL is often just spelled B-A-L-L.
Notes: