The only thing you want to worry about during a tennis match is your game. Gear issues are an unwanted distraction. At the end of the day, you want to perform at your best without any concern for minor details regarding your shorts.
The ideal t-shirt is light, moisture wicking and comfortable around the shoulders and neck area without being overly baggy.
Try: adidas Barricade Crew Shirt
This is probably the lightest shirt I've ever worn. The polyester blend with adidas's Climacool Formotion technology makes it absorb sweat while maintaining a light feeling. At no point did I feel it was restricting my movement or too heavy from sweat.
When it comes to shorts my criteria are above the knee and light thin material.
Try: adidas Barricade Shorts
These fit just above the knee while maintaining a light and moderately thin profile. The pockets are deep so balls never slip out when you move. The shorts maintain their lightness throughout the duration of a midsummer practice.
Two elements are key when it comes to shoes: weight and durability.
Try: adidas Barricade II
This shoe is a bit heavier than other tennis shoes, but its durability is second to none. These shoes comes with a six-month warranty on the outsole. I put them to the test training four hours a day, and they lasted around eight months. (Shop smart; see How to Find the Best Tennis Shoe Deals.)
If you're looking for a lighter shoe, Nike's tennis shoes may be a better fit. Babolat shoes are similar to adidas shoes in comfort and durability, but they add a bit of cushioning around the top of the foot, which some players prefer.
Never wear full cotton. While working for four years in one of the top running shoe stores in the country, I learned that wearing cotton socks causes blisters. Cotton absorbs sweat, causing friction that can lead to blisters. A polyester, nylon and cotton blend is what most tennis socks are made of. That is a perfect mix, and I have never had a problem with blisters wearing them.
Headbands and wristbands
Any kind made with cotton will prevent sweat from reaching the eyes and hands during competition. The bandanas are Dri-Fit and work just fine as well. My new favorite type of headband is what cross country skiers wear.
Try: Madshus Lycra headband
This is light, comfortable and absorbs sweat better than any piece of headwear I have ever worn.
Probably the most important part of a tennis racquet. Depending on the location, a tacky grip or a grip such as the Tourna grip are my recommendations.
Try: Wilson Pro Overgrip
This is my personal favorite for dry, low-humid conditions if you sweat a lot. If you live in a hot or humid environment, I strongly recommend the Tourna grip. It's second to none in absorption and durability.
Now that you bought it, keep it clean; see Clean Gear For Healthy Athletes.