When you have rwached Province 18 in Season 1, XP will start at 2K. If you wish to replay this province to quickly level up your rank, you will need a powerful team with at least all your heroes are Rare type, and PREFERABLY HIGHER HP and NOT EASILY LOSE HP (more defensive I should say). Spare as much food as you could (higher level mills) to upgrade your Heroes, prepare HP potions (the red ones) and upgrade Troops.