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Gymnastics Rings
These are the gymnastics rings I recommend. I like them because they are inexpensive but also good quality. The buckle that is used is large and strong, whereas most of the buckles that come with rings on Amazon are small and cheaply made. YOU DON'T WANT THE BUCKLE TO BE CHEAP. It's important that your buckle is sturdy to keep you safe at all times.
Gymnastics rings are the only things you really need for exercise. They provide the perfect combination of muscle building, improved mobility, and the prevention of injury - the three most important things for a hitter to consider when developing a training program. Plus, they don’t require you to depend on weight rooms, which aren’t always available. They also work the exact muscles you want to build for the swing - upper arms and back and forearms - but do so in a way that doesn't require movements that simulate the swing which would thereby risk repetitive movement injury and burnout. Find a tree at your local park to hang them, or hang them from a sturdy pull-up bar.
Juggling Balls
Good size and shape. Most juggling balls are awkwardly shaped and too small. Taylor gets it right. She's also a great teacher of all sorts of juggling tricks. I learned how to juggle five balls from her videos.
Camera and Iphone Tripod for Filming Swing
When filming, the phone should be at about hip height. You could set up your phone on the tripod and keep the remote in your pocket and start and stop video when you want, without having to go back and forth to your phone. I like this idea because I don't think you should be analyzing video at the same time that you are hitting balls, so not going back to the camera will preclude you from being tempted to view the video at that moment. Just be sure you talk into the camera about what you are working on before you swing so you know what to look for when you are analyzing later on.
I chose this tripod because the legs reach wide, so on windy days it will hold its place. I also like it because it is sturdier than many of the tripods sold on Amazon. It will take a beating since you are lugging it around with other sports equipment.
Gardening Gloves
I know what you're thinking, "What would I want gardening gloves for?" Well, first off, you don't need them. You don't NEED anything on this page. These are just inexpensive ways of making your practice time more efficient. I first got the idea of using gardening gloves from reading about one of my favorite basketball players as a young man, Jason Williams. He had unbelievable ball-handling skills, which he developed in large part because he wore gloves while dribbling as a kid. Wearing gloves would take away much of the feel in his hands, so when he took the gloves off, he had much better control of the ball. Genius.
I use these gloves for putting and chipping practice, juggling practice, and also dribbling basketballs. As a baseball player, you could also use these gloves for hitting, fielding ground balls, and throwing. It makes pretty much any athletic endeavor much harder to do by taking away the feel in your hands, so when you take them off, your coordination for the move will be supercharged. Regular practice using these gloves will substantially increase the rate at which you improve your skill in an athletic movement. This is a huge hack that exactly none of your competition is doing, I promise you.
I also use these gloves to cover the hands and forearms from the sun. That way I can take my shirt off and get sun on my torso which needs it much more than my forearms and hands, which, being a baseball player and golfer most of my life, have gotten their share of sun through the years. So these gloves have a dual-purpose. They stay in the passenger seat of my car. I use them a lot.
Fat Grips
This idea was given to me by a college player named Cal Elvis. Place the fat grip over your back hand grip, to disable the back arm and hand from contributing as much. This is a great way to find a new structure to your swing, one that involves not overexerting the back arm.