No. A dampener changes the sound and the feel of the string bed, which many players prefer, but it does not meaningfully reduce the shock reaching your arm. If you are dealing with arm pain, string type, tension and racquet choice matter far more.

It adds weight wherever you put it. Tape at three and nine o clock adds stability and a bigger effective sweet spot. Tape at twelve o clock adds power and swingweight. Tape in the handle adds weight without slowing the swing. Small amounts make a noticeable difference, so add a little at a time.

Pressurised balls lose their bounce within a few hours of play once the can is opened, and they slowly go flat on the shelf even unopened. Pressureless balls last far longer and are the better choice for ball machines, baskets and practice.

A spare overgrip, a spare set of strings if you break them, a dampener if you use one, a sweatband, and more balls than you think you need.