Reputation represents the level of competitiveness of each Friendly Championship. Each team has its own reputation that adds up to the overall reputation of the whole Friendly Championship.
Reputation is calculated for each team individually and overall for the whole Friendly Championship. The individual reputation is calculated based on your Team OVR on your club level, and it is calculated when a Manager applies for a Championship. It stays the same for that season. The overall Friendly Championship reputation is calculated based on the individual reputations of the top 7 clubs on the leaderboard.