Audition House heh.

There's three solutions to this:

1. Place an item for max gil on your retainer once you get a spot, so it never gets kicked out.
2. Move your retainer to Limsa or Gridania and take a huge penalty on how many customers you have.
3. Shout about your wares.

The MW system will likely not see any huge improvement until 2.0 is out with the auction house. It makes little sense now with the new version being only about half a year away.