Chapter 2 introduces slightly tougher enemies and your first mini-boss encounters. You'll start to feel the importance of a balanced team composition. Consider adding a dedicated healer if you've pulled one (e.g., Custard Cookie III is good for early game, but a better healer like Herb Cookie or Pure Vanilla Cookie would be ideal if you've acquired them). Continue to level up your Cookies and upgrade their skills.
This chapter also introduces more complex production chains in your Kingdom. You'll need to start producing items like Sturdy Sawblades and Radiant Sugar Cubes, which require multiple steps. Keep your production buildings busy to avoid bottlenecks in your progress. check the 'Quests' tab for ongoing objectives that reward you for completing stages and Kingdom tasks.