The G15 has 2 Built-In USB ports, im not sure if there 1.1 or 2.0, but you said that there 1.1, so lets go with that. You do not need to buy a new USB hub, if its 1.1 and you have 2.0, it will simply just go slower. And if you have 1.1 and its 2.0, it will still run, but slower.
With a keyboard USB 1.1 is fast enough, but i wouldnt plug anything into the keyboard such as a flash drive, i would only use it for a mouse, joystick, wheel, ect.