In order to gain ranks quickly you
must play opponents of the same rank as you are, same as it is in the
arcade version. When defeating CPU opponents of the same rank as your
character it usually only requires 3 to 5 wins to get a promotion.
After your fight has ended in Arcade Mode you can select on of 3
opponents with the directional pad, you can't always select an opponent
with the same rank but do so when one is available. You'll have your
character rank maxed out in no time.