When you search for a ranked room and you don't automatically connect to an opponent it will make a room instead. After that it will say "Looking for tier X opponent", X being your tier. --- "Synchro Chip, Slot-in, Cross Fusion!" Wargreymon: Level 126
This is all postulation at the moment, but I believe your Tier is related to your rank on the leaderboards. I've been rank 130-160 for weeks, and I've never left Tier 6, and on another thread, a guy was at Tier 4 around rank 1000.