You may upgrade your bonuses through the actions menu under Spend Cash Credits.  You may also eat any of the Chicken NPC's edible eggs to increase your bonuses.

Skill Chance Bonus
  • Increases your chance of earning a skills.
Credit Bonus
  • Increases the amount of credits dropped from monsters and credit bags.
Experience Bonus
  • Increases the amount of experience you earn from monsters
  • At 250% Experience Bonus you no longer lose your overflow experience and instead store it to level with any action performed.