Grind your robots at the easier patrol level (the less money required) to gain experience and leveling. As the same time, the easier stage has low mortality rate. Later on, once the robots reach higher lvl and you also have optimized the robot population, it is more easy to complete a harder mission.

Try not to lose, if you think you are going to for the next round, then select "retreat" to avoid loosing your alliances (if you lose, you will also lose your alliance who is accompany with you to patrolling)