I did my PhD (mapping and studying the physics of caves in the ice on an antarctic volcano) purely for fun, and it was awesome.

I hope you have a similarly rewarding experience. You will encounter unfair systems and unscrupulous people, and it will be frustrating. The data will be confusing as hell. My only advice is stay true to yourself. Maybe look into some of the new trends that could fix academia -- pre-registration, open access with public comment periods, reproducible code, etc. For inspiration, I cheer for crusaders like Data Colada who are trying to save the academic system.