Have the player do missions to gain small rewards around the game. Either mission points that you can spend in a special store or maybe cash rewards or donator points. 

Missions can be things like :

collect five bounties in the next 24 hours

Send out four expeditions 

Acquire/farm X amount of certain item

Good idea 👍

Thumbs up simply for suggesting something to further incentivise people to do expeditions and other jobs than only robberies.
IMO, it should either be daily missions (if you want a 24-hour limit), weekly missions (if it's a mission that might need longer time), or an opt-in where you would have to accept a mission (with a set time limit, which could be maybe 1, 3 or 5 days).