Racquet first, strings second, shoes third, balls fourth in importance. I’m pretty organized and have strong preferences for everything else I buy too that are in my tennis bag, but those are the only four things that really affect how I play.
The combination of Babolat Pure Strike Tour, VS17/HyperG18 at 47/44, Asics GR8 shoes and ProPenn XD balls have carried me to a lot of wins on hard courts. I also like Lacoste tennis clothes (tops/polos/shorts), Nike tennis shorts, Adidas/Babolat polyester hats, Tecnifibre/Kirschbaum/Volkl overgrips, Thorlo thick socks, Babolat Vibrakill dampener, Nike/Adidas nylon doublewide wristbands, Oakley non-polarized sunglasses, Clif Shotblox energy chews, Dunlop 12-racquet black bag and an Under Armour gallon water bottle.