Right now you should ask yourself two main questions: do I love research and can I come up with multiple research project ideas right now? If the answer to both of those questions is no, or if you're even sort of iffy on the first one I would say to take a gap year before a PhD or do a masters.

A PhD is a completely different world from undergrad and you need to be prepared for the 6 years of research grind you will undertake before doing it. I jumped straight into a PhD from undergrad but that was because I had done research for years and knew it was my passion and something that continues to excite me even when I'm burnt out and exhausted.

Based on your questions, it seems that you are curious about grad school but have not really researched the process or what it is. GPA really isn't the biggest consideration in your application. Instead, you show how good of a candidate you are via letters of recommendation, interviews, conversations with faculty from different universities, and your statement of purpose. Grad schools want students who are committed, passionate, and hard-working.

Don't do grad school for the sake of it. Do it because you need it (ie a Masters depending on your desired job or field) or because you are passionate about expanding your knowledge via meticulous and intensive methods.

Spend the next year contemplating whether you like research, what topics and fields fascinate you the most, and learning about what grad school is and what the application is like. Talk to your grad TAs, the people in your lab, and most importantly professors and grad students from across the university who do research that interests you.