pretty much the same as relationships. depending on enneagram types, personal needs, overall imbalances, subjective experiences, other relationships, etc.
N dom first and foremost. 4w3 is fun for me as a 5w4, aesthetically i dig it. other 5w4s, 7w6s, and 4w5s all play a huge role in my own self-understanding.
inps too. infp 4w5 is one of my favorite artistic types (4w5 is the best type at self-understanding and contemplating the widest range of internal complexity). 4w3s have fucking artistic flare, their styles seem so effortless bc of that 3 image-control/impression-management (a la whitman, proust, wilde, etc). 9w1 infps offer the greatest form of love (my most common type). i have learned how to show them i recognize the gifts they bring to others as teachers and as healers. intps are great when they're stoned, flexible, and capable of some Ne movement. otherwise they get as fixated and judgy as any unhealthy ip dom Ji. which gets exhausting. 5w6 offers sooooo much knowledge and 5w4 has the same interest in composition that i do. 6s are loyal and trusted friends which matters in some cases more than anything else.
enjs somewhere down the line. i probably get along with istjs more easily, i know how to use their strengths and how to help get them re-focused or relaxed when they need it. enjs i don't have as much experience with so i don't see how to make it work as well. plus e2 and e1 are generally less overlapping with my interests. the worst types for me are 3w2, 3w4, 8w7, 8w9. when i am healthy i can learn from 3w4 which is my arch nemesis. 7w8 and 9w8 and i sometimes butt heads.
after that probably istjs, whose methods for problem-solving and resolve i totally respect. plus subjective experiences, family members, etc.