That's hard. But you can win using only the coins Rin provides.

1) Keep chaining together three coin combinations.
2) As a rule of thumb, try and use your highest value coins (7's, 8's, and 9's) because they will be disappearing soon.
3) Don't worry about the special properties of the coins. This match is too hard to take into account whether you're losing 50 gil or not.
4)Pray to whatever god you worship he doesn't produce a lot of 1's.