It can be pretty annoying having to wait for a Ranking Match in arcade. They can often be 10 battles apart. There is a trick however which often works to trigger a Ranking Match. At the end of each battle you are given a choice of 3 characters to fight in your next match. Pick the character with the same ranking as you. For example if you're at 8th Kyu pick the character which is also at 8th Kyu. This does not gaurentee a ranking match, however if you beat him your next battle will more likely be a ranking match. Often the 3 choices given to you does not include a character of equal ranking to you. In this case you should pick a character higher in rankings.