A move that is easier to understand its concept than ExtremeSpeed, despite it's smaller damage. Quick Attack is a priority move, useful when the opponent is faster than the user, or when the opponent's health is low, or when it is the reverse.
It is a good idea to choose Riolu and Eevee, for it is a Pokemon that is greatly reliable in battles. When training these two, maybe a nice technique to use is to place a stronger Pokemon at the leftmost slot of your party, and when you send this powerful Pokemon out, do some damage on the opponent, then switch out with them, using the said move. See how useful it is?