Bearings are a must-have upgrade if you're going for anything above stock....even stock they're a great upgrade! But going with faster motors means you're spinning things a lot faster, so with bushing you're really holding yourself back.
Stock, the T3 came with a LRP Runner speedo and an ok closed endbell 20t motor. Start with the bearings (you can find complete bearing kits out there), and then upgrade to a better mod motor. The LRP Runner can handle motors down to 17t...and the good thing about the LRP ESC's is that they all come with a lifetime warranty.
Also, if you're going to get into any kid of racing, it might be a good idea to upgrade the radio. The stock one works, but it's pretty cheesy and can't do any very accurate adjustments.
Good luck and have fun!