I have a great "first real bike" for a girl (or boy if they don't mind the hot pink color). It is a Marin Hidden Canyon w/ 20" wheels, frame size XXS. I would say that the target age would be 5-8 years old. It is a 2X7 with a mixture of original Shimano and SRAM components. I great introduction to geared bikes that can actually be used for real trail-riding.