Going from bottom to top:
5. The Night Circus by Erin Morgenstern. Basically all the people of the Circus. They are all so quirky and great. I love how they all tie their shows together to create the circus.
4. Miss Peregrine's Home for Peculiar Children by Ransom Riggs. It would be so great to be a part of this group. They are all so quirky and strange but also know how to have fun and stick together.
3. Red Rising by Pierce Brown. Darrow and his Howlers are great. They band together during at the Institute but those bonds are even deeper as we see in Golden Son. And there is also Severo and Mustang who to add to Darrow's group of friends. He may be a Red in disguise but he has made many friends with Golds. I may never be able to fight like the Howlers but I love their loyalty towards Darrow.
2. Fangirl by Rainbow Rowell. I love the relationships between Cath and her sister, Wren, Reagan, her roommate, and Nick (when he isn't being obnoxious). This one may not fit exactly but I do not care. The people around Cath are great and that is good enough for me. Another reason this ranks so high is that Cath reminds me so much of myself.
1. Harry, Ron, and Hermione from the Harry Potter Series. Should be absolutely no surprise! These three are the pinnacle of a great friendship. They show how all you need is a few close friends (they do have others who play important roles, but at the end of the day it is the trio).
Let me know what your favorite friend groups are in the comments!