The more badges you earn, the more things you can purchase from Salesman Rick. Buy Manipulator Chips to collect lots of Mortys. The overall difficulty of the Morty trainers and each world's Rick depends on how many badges you have earned. To keep the difficulty manageable, wander around a world fighting trainers, but not Rick, in order to level-up your Mortys. Then, intentionally lose a battle to return to the Citadel and repeat the process.