What should I do over the summer to make me a better candidate?

Hi all, first time posting here. I go to school in the midwest (semi-target) but I live in the northeast. Just finished up my freshman year to mixed feelings. Finished with an okay GPA of 3.7, but I didn't really apply myself outside of what was required. Regardless I'm driven to make some changes this summer and have enrolled myself in the Google Data Analytics Certification course whilst also studying up with the Joshua Rosenbaum textbook. I'm working at a gym but it's more of a summer gig just to keep me busy. Beyond this, what else should I do? I'm intrigued to apply to some fall internships but beyond that I'm lost for the summer.

Any feedback or suggestions would be greatly appreciated.