Repeatedly select the "Try Another" option until you matched with someone who is about the same level or lower than you. After winning a match, you will get two stars until you lose. Because you can never lose a rank, attempting this against slightly tougher opponents is fine. Ignore their PvP Rank, as it does not indicated anything important. However, losses will cost gold. Note: You can pay for souls and level your minions without actually leveling your hero. Additionally, manual defense fights that are won will also count as PvP victories and also advance your rank.