ive noticed a big difference between the Cs. they all sound "the same" but some are higher the same and some are lower the same. you can even play them at the same time and they cooperate very well. next step please
go to the middle of the keyboard. take every white note from C to the next C. so that should be 8 notes (c, d, e, f, g, a, b, c). Now, see what songs you can play! just using those notes. hint: start with like popular kids songs