In a traditional mobile RPG game, you only get treasure when you kill all the bad guys. This is not the case in Mr Football, as merely playing a match earns you rewards, both in currency and development for you and your players.
Most game modes carry some coach development points (DP) to raise your accreditation level, which is very important to raise your salary cap level at the club. Many modes will also provide soft currencies of credits and/or fame and occasionally a bonus of tickets or rubies]. The Origin mode also rewards you with coins from the various regions.
Some modes will reward you with trainer tokens for a full game, but in Campaign you will get a lot more trainers from walkovers. This is because when you play out a full match your selected players earn experience points (XP) for playing, but in walkovers you do not choose a team so trainers are given in compensation.
Campaign is also the mode where you earn the most equipment. This is particularly important for player development, as certain items of equipment are only available by beating a small number of opponents.